Sulfonyl-based electrolyte solvent, electrolyte prepared using the same, and electrochemical device prepared using the electrolyte

Abstract

The present invention relates to a sulfonyl-based solvent system for an electrolyte used in electrochemical devices such as secondary batteries. In some embodiments, the solvent system of the present invention comprises a sulfonyl (-SO2-) based solvent optionally combined with one or more different sulfonyl-based solvents and / or one or more non-sulfonyl-based solvents. Five exemplary chemical formulas of sulfonyl-based solvents usable in the sulfonyl-based solvent system of the present invention are disclosed. Additionally, an electrolyte comprising one or more salts, such as one or more alkali metal salts, dissolved in the sulfonyl-based solvent system of the present invention is disclosed. Suitable formulations of the disclosed electrolyte may provide one or more advantages, including but not limited to improved cycle life, improved low-temperature operation, and reduced flammability.

Description

Technology Field

[0001] Related application data

[0002] The present application claims the benefit of priority to U.S. Provisional Application No. 63 / 077,305, filed September 11, 2020, titled “Class of Sulfonyl-Type Electrolyte Solvents, and Electrolytes Made Therewith and Electrochemical Devices Made Using Such Electrolytes”; U.S. Provisional Application No. 63 / 106,467, filed October 28, 2020, titled “Class of Sulfonyl-Type Electrolyte Solvents, and Electrolytes Made Therewith and Electrochemical Devices Made Using Such Electrolytes”; and U.S. Provisional Application No. 63 / 162,634, filed March 18, 2021, titled “Class of Sulfonyl-Type Electrolyte Solvents, and Electrolytes Made Therewith and Electrochemical Devices Made Using Such Electrolytes”, the full text of each of which is incorporated herein by reference.

[0003] Field of the present invention

[0004] The present invention generally relates to the field of electrolytes for electrochemical devices. In particular, the present invention relates to a sulfonyl-based electrolyte solvent, an electrolyte prepared using the same, and an electrochemical device prepared using the electrolyte. Background Technology

[0005] Given the low Coulomb efficiency (CE) of Li plating / stripping based on conventional electrolytes, the progressive growth of lithium dendrites, and the poor cycle life of high-energy Li metal batteries (LMB), some achievements in the discovery of new electrolytes will be required. Despite high oxidation stability for cathodes up to 4.5 V, conventional carbonate-based electrolytes designed for early lithium-ion batteries do not work well with lithium-metal-anode rechargeable batteries due to severe lithium dendrite formation during lithium metal plating / stripping cycles. Highly concentrated carbonate-based electrolytes improve the lithium plating form but remain undesirable due to high reductive reactivity to the lithium metal anode, resulting in low lithium metal cycle CE and short cycle life. Ether-based electrolytes exhibit better chemical stability for lithium metal, and highly concentrated ether-based electrolytes, including locally concentrated ether-based electrolytes, can extend the oxidative electrochemical stability window of the ether to up to 4.3 V, thereby significantly improving the cycle life of 4 V lithium metal rechargeable batteries. However, ether-based electrolytes have an inherent weakness due to the low oxidative stability of ether functional groups, which can be easily oxidized by uncoordinated solvents at high voltage (>3.5 V) cathode surfaces, particularly at high temperatures (>45 °C), leading to excessive cell impedance growth and cell failure. Both commonly reported carbonate-based and ether-based electrolyte systems have disadvantages and limitations for lithium metal rechargeable battery applications.

[0006] Improving the thermodynamic / kinetic stability and oxidative stability of next-generation LMB electrolytes for Li anodes at high voltages is difficult but important, and this is directly related to the further development of high-energy LMBs for various applications, particularly in electric vehicles (EVs). Therefore, finding an alternative electrolyte solvent system that is compatible with lithium metal anodes, effectively passivates them, and is simultaneously oxidatively stable at high voltage cathodes (> 4V) is desirable for achieving long cycle life of lithium metal anode cells.

[0007] Compared to various solvents known for rechargeable LMBs (e.g., common carbonate and ether solvents), a new class of sulfonyl solvents can theoretically exhibit better antioxidant performance at higher voltages during battery charging and possess more efficient passivation capabilities for Li metal anodes. Recently, electrolytes composed of LiFSI and LiPF6 salts and a single N,N-dimethylsulfamoyl fluoride (DSF) solvent have been reported to improve battery cycling. However, the reported Coulomb efficiency (99.03%) of Li plating / stripping in LMBs obtained with this single sulfonyl-based electrolyte is still unsatisfactory. Furthermore, there are some undesirable characteristics of DSF itself, such as poor coordination with most salts that promote high solvent volatility, very unsatisfactory oxidation stability, a high melting point causing limited low-temperature performance, high cost due to dissolved high-concentration salts, high viscosity, and lack of flame retardancy. means of solving the problem

[0008] In one embodiment, the present disclosure relates to an electrolyte for an electrochemical device having an alkali-metal anode having an anode-active material comprising an alkali metal. The electrolyte comprises a sulfonyl-based solvent system comprising one or more sulfonyl-based solvents (wherein each solvent has one of the following general molecular structural formulas: Structural Formula 1: R1-SO2-R2, wherein each R1 and R2 is -F; -CF3; -N(SO2F)2; -N(CH3)SO2F, -N[(CH2) x CH3)][(CH2) y CH3)] (x = 0 to 3, y = 0 to 3); -N[(CH2) x CH3][(CH2) y CH=CH(CH2) z -H] (x = 0 to 2; y = 1 to 3, z = 0 to 3); -(CH2) x CH=CH(CH2) y -H (x = 0 to 3; y = 0 to 3); -C6H 5-x F x (x = 0 to 5); -(CH2) x (CH 2-y F y ) z CH 3-w F w (x = 0 to 2, y = 1 to 2, z = 0 to 2, w = 0 to 3); -(CH2) x (CH 2-y F y ) z F (x = 0 to 2, y = 0 to 2, z = 0 to 2); and -(CH2) x CH=CH(CH 2-y F y ) z F can be one of (x = 0 to 3, y = 0 to 2, z = 0 to 2); and R1 ≠ R2 or R1 = R2; Structural Formula 2: -R3-SO2N-R5SO2-R4-, where each R3 and R4 is -CF2; -CH2-; -CH((CH2) x H1-y F y )- (x = 0 to 3, y = 0 to 1); -CF((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1); and -CH((CH 2-x F x ) y CH=CH 1-z F z (CH 2-x' F x' ) v H 1-w F w )- (x = 0 to 2, x' = 0 to 2, y = 0 to 2, z = 0 to 1, v = 0 to 2, w = 0 to 1) may be one of; R3 ≠ R4 or R3 = R4; and R5 is -(CH2) x CH3(x = 0 to 3); and -(CH2) x CH can be one of CH=CH2(x = 1 to 3); structural formula 3: -R6-SO2N-(R8)R7-, where each R6 and R7 is -CF2-; -CH2-; -CH((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1); -CF((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1); and -CH((CH 2-x F x ) y CH=CH 1-z F z (CH 2-x' F x' ) v H 1-w F w )- (x = 0 to 2, x' = 0 to 2, y = 0 to 2, z = 0 to 1, v = 0 to 2, w = 0 to 1) may be one of; R6≠ R7 or R6= R7; and R8-(CH2) xCH3(x = 0 to 3); and -(CH2) x It can be one of CH=CH2(x = 1 to 3); Structural Formula 4: R9-SO2N-(R 10 )(R 11 ), where, R9 is -(CH2) x (CH 2-y F y ) z F can be (x = 0 to 2, y = 0 to 2, z = 0 to 2), and R 10 -(CH2) x O(CH2) y CH3(x = 2 to 4, y = 0 to 2) can be, and R 11 -(CH2) x CH3(x = 0 to 3) or -(CH2) x O(CH2) y CH3(x = 2 to 4, y = 0 to 2) may be; R 10 ≠ R 11 or R 10 = R 11 ; and structural formula 5: R 12 -SO2-R 13 , here, R 13 Within, there are nitrogen (N)-containing, oxygen (O)-containing, hydrocarbon-only-containing, or (N+O)-mixture-containing ring structures; R 12 -(CH2) x (CH 2-y F y ) z F (x = 0 to 2, y = 0 to 2, z = 0 to 2) and; R 13 -N(CH2)4(1-pyrrolidino 5-membered ring); -N(CH2)5(1-piperidinyl 6-membered ring); -N(CH2CH2)2O(4-morpholinyl 6-membered ring); -C5H9(cyclopentane); -C6H 11(Cyclohexane); -C4H7O(2 or 3-tetrahydrofuran); and one of its fluorinated analogs) and one or more alkali metal salts dissolved in one or more sulfonyl-based solvents, wherein the alkali metal salts have cations comprising the alkali metal of the anode active material; wherein the electrolyte contains a single solvent, and the single solvent has structural formula 1, the case where structural formula 1 is -N(CH3)2 with respect to the case where R1 and R2 are either -F or -CF3.

[0009] In another embodiment, the present disclosure relates to an electrolyte for an electrochemical device having an alkali-metal anode having an anode-active material comprising an alkali metal. The electrolyte comprises a hybrid sulfonyl-based solvent system comprising: a first solvent which is a first sulfonyl-based solvent; and a second solvent selected from the group consisting of a second sulfonyl-based solvent and a non-sulfonyl-based solvent; and at least one alkali-metal salt dissolved in the hybrid sulfonyl-based solvent system, wherein the alkali-metal salt has a cation comprising the alkali metal of the anode-active material. Brief explanation of the drawing

[0010] To illustrate embodiments of the present invention, the drawings show aspects of one or more embodiments described herein. However, it should be understood that the present invention is not limited to the exact arrangements and means shown in the drawings. Figure 1a is a graph of capacity retention for the number of cycles showing the higher cyclic stability of an anode-free pouch cell using an electrolyte containing the hybrid sulfonyl-based solvent system of the present invention versus the cyclic stability of an anode-free pouch cell using an electrolyte containing the hybrid sulfonyl-based solvent system. Figure 1b is a graph of the Coulomb efficiency of the anode-free pouch cell shown in Figure 1a. FIG. 2a is a graph of capacity retention versus cycle count for pouch cells including a lithium-metal anode and a Li / NMC811 cathode, one pouch cell using an electrolyte containing the hybrid sulfonyl-based solvent system of the present invention and the other pouch cell using an electrolyte containing a non-hybrid sulfonyl-based solvent system. Figure 2b is a graph of Coulomb efficiency versus number of cycles for the pouch cell of Figure 2a. Figure 2c is a graph of charge capacity versus number of cycles for the pouch cell of Figure 2a. Figure 3 is a hybrid graph showing the salt-solvent molar ratio versus volume ratio and salt molar concentration versus volume ratio for an electrolyte comprising a hybrid sulfonyl-based solvent system composed of LiFSI, DSF, and EMSF under the upper limit of salt solubility at 10°C. Figure 4 is a graph of heat flow versus temperature from differential scanning calorimetry of a plurality of electrolytes and a solvent system comprising only DSF, comprising the DSF-EMSF hybrid sulfonyl-based solvent system of the present invention. Figure 5 is a graph of current density versus potential from linear-sweep voltammetry (LSV) scans for ether-based and sulfonyl-based electrolytes, showing lower oxidation current density of the sulfonyl-based electrolyte at higher temperatures and higher voltages compared to the ether-based electrolyte. Figure 6 is a graph of current density versus potential from LSV scans for a hybrid sulfonyl-based electrolyte and a single sulfonyl-based electrolyte, illustrating the superior oxidation stability of the hybrid sulfonyl-based electrolyte compared to the single sulfonyl-based electrolyte. Figure 7 is a graph of current versus voltage from cyclic voltammetry (CV) using an aluminum electrode for the ether-based and sulfonyl-based electrolytes of Figure 5, illustrating the passivation of the aluminum electrode after one cycle for both electrolytes. Figure 8 is a graph of current versus voltage from a CV using an aluminum electrode for the hybrid sulfonyl-based electrolyte and the single sulfonyl-based electrolyte of Figure 6, illustrating faster passivation of the aluminum electrode by the hybrid sulfonyl-based electrolyte than by the single sulfonyl-based electrolyte. Specific details for implementing the invention

[0011] Regarding lithium-metal batteries, a key technical issue is that cycle life is limited in most conventional electrolytes due to the low Coulomb efficiency (CE) of the lithium anode during cycling. Additionally, while some conventional electrolytes are stable for lithium metal anodes, they are oxidatively unstable for 4V cathode materials, particularly at temperatures higher than room temperature (~20°C). Some conventional electrolytes can maintain a liquid phase and conductivity at room temperature and high temperatures (e.g., >45°C), but they do not function properly at low temperatures (e.g., <0°C) due to phase separation and freezing.

[0012] To address these and other problems, the novel sulfonyl-based electrolyte disclosed herein exhibits fewer side reactions with lithium, reduces the lithium stacking surface area, significantly increases the CE of lithium plating / stripping, inhibits lithium dendrite growth, minimizes oxidative decomposition of solvent(s) at high voltage (>4.5V) and high temperature (>45°C), and extends the liquid state temperature range, either alone or in various combinations, thereby greatly improving cycle life and high / low temperature stability. The cyclic stability of the novel sulfonyl-based electrolyte has also been verified in various test protocols. By combining the novel class of sulfonyl-based solvent systems disclosed herein with electrolyte formulation designs, lithium metal cells and batteries relying on these novel sulfonyl-based solvent systems have demonstrated long-lasting cycles, high energy density, and improved safety.

[0013] Before proceeding with further detailed explanation, throughout this disclosure, when used with a corresponding numerical value, the term “about” refers to ±20% of the numerical value, generally ±10% of the numerical value, often ±5% of the numerical value, and mostly ±2% of the numerical value. In some embodiments, the term “about” may refer to the numerical value itself.

[0014] In some aspects, the present disclosure relates to a sulfonyl-based solvent system used in electrochemical devices, particularly primary and secondary batteries and supercapacitors. The sulfonyl-based solvent system of the present disclosure is particularly effective when used in a secondary alkali-metal-metal battery (AMMB), such as a lithium-metal battery (LMB), wherein the anode is of a non-intercalating type and comprises an alkali metal (e.g., lithium (Li), sodium (Na), potassium (K)) or an alloy thereof as the anode active material.

[0015] In connection with the present disclosure and the appended claims, the terms "sulfonyl-based solvent" and similar terms refer to each oxygen atom and a sulfur atom (O=S=O), two substituents, R n It means a solvent comprising a molecule having one or more sulfonyl (-SO2-) groups having a double bond between a nitrogen atom bonded to at least one SO2 group (n=2), and optionally, a molecule having one or more sulfonyl (-SO2-) groups. In some embodiments, the sulfonyl-based solvent system of the present invention comprises a single sulfonyl-based solvent that may or may not comprise one or more non-sulfonyl-based solvents. In some embodiments, the single-sulfonyl-based solvent system may comprise a modified molecular structure of a conventional commercially available sulfonyl-based solvent, such as N,N-dimethylsulfamoyl fluoride (C2H6FNO2S, DSF). In some embodiments, the sulfonyl-based solvent system of the present invention comprises two or more sulfonyl-based solvents of the present invention that may or may not comprise one or more non-sulfonyl-based solvents. Note that where the sulfonyl-based solvent system comprises two or more sulfonyl-based solvents of the present disclosure, for example, the solvent system is described herein as a "hybrid sulfonyl-based solvent system." Detailed examples of the chemical structures of the sulfonyl-based solvents of the present invention are presented below.

[0016] In some aspects, the present invention relates to electrolytes prepared using the sulfonyl-based solvent system of the present invention, which are referred to as "sulfonyl-based electrolytes" for convenience in this application and the appended claims. The sulfonyl-based electrolytes of the present invention comprise the sulfonyl-based solvent system of the present invention, one or more salts suitable for the intended electrochemical apparatus, and optionally one or more other components, such as one or more additives added to improve one or more properties or characteristics of the sulfonyl-based electrolytes. In relation to AMMB, each salt generally contains a relevant alkali metal as a cation. Non-limiting examples of salts and salt combinations for use in the sulfonyl-based electrolytes of the present invention are shown below.

[0017] The advantages of AMMB containing LMB resulting from the use of the sulfonyl-based electrolyte of the present invention include the following, individually and / or in various combinations depending on the situation at issue. The sulfonyl-based electrolyte of the present invention, with its extremely high stability for alkali metal anodes (e.g., Li-metal anodes) (e.g., alkali metal (e.g., Li) plating / stripping Coulomb efficiency (CE) > about 99.0% or even > about 99.5% or higher) and high antioxidant capacity (e.g., oxidation voltage > about 4.3V or even > about 4.8V), can lead to improved cycling performance compared to AMMB containing LMB using only conventional non-sulfonyl-based solvent systems. Through the molecular design of a new class of sulfonyl-based solvents as disclosed herein, newly discovered sulfonyl-based electrolytes comprising a single sulfonyl-based solvent system or a hybrid sulfonyl-based solvent system can provide very high chemical and electrochemical stability, enhanced wide-range temperature performance, non-flammability, low cost, high safety, and excellent compatibility with cell fabrication and processes at the cathode and anode of AMMBs such as LMBs. The sulfonyl-based electrolytes of the present invention are particularly useful for AMMBs, but their applications are not limited thereto.

[0018] As mentioned above, in some embodiments, the sulfonyl-based solvent of the present invention may comprise a modified version of DSF. For example, one route to improve the oxidative stability of DSF is to replace the electron-donating amine group -N(CH3)2 of DSF with an organic group having low electron-donating ability, such as a saturated or unsaturated hydrocarbon group (e.g., alkyl, alkene, alkyne, or aromatic group, with or without fluorosubstituents), or to replace one or more of the methyl groups with electron-withdrawing substituents (e.g., fluorosubstituted alkyl group, oxyalkyl group). For example, the melting point of DSF can be lowered by replacing the symmetric -N(CH3)2 amine group of DSF with an asymmetric group such as the -N(CH3)(CH2CH3) group, thereby producing N-ethyl, N-methyl sulfamoyl fluoride (EMSF) and lowering the melting point of DSF from -16°C to -65°C, and for example, the melting point of DSF can be lowered by replacing the -N(CH3)2 group in DSF with a longer hydrocarbon-based substituent such as -N(CH2CH3)2, thereby producing diethylsulfamoyl fluoride (DESF) and lowering the melting point of DSF from -16°C to -35°C. In addition, bis(2-methoxyethyl)sulfamoyl fluoride (BMSF) obtained by replacing two methyl groups on the -N phase with two methoxyethyl groups has the advantage of increasing the boiling point (290°C) and lowering the melting point (-37°C), thereby providing a wide operating temperature range for BMSF-containing electrolytes.

[0019] The interaction between the sulfonyl-based electrolyte of the present invention and the alkali-metal anode of the AMMB, such as the lithium-metal anode of the LMB, forms a solid electrolyte interface (SEI) layer on the alkali-metal anode, thereby protecting the alkali metal during battery operation similarly to conventional electrolytes that form an SEI layer. A similar cathode electrolyte interface (CEI) layer can likewise be formed on the cathode of the AMMB. To further enhance the stability of the SEI layer and / or CEI layer, unsaturated organic groups that can serve as precursors for forming organic polymers in combination with inorganic components formed on the electrolyte / electrode interface can be introduced into the structure of the sulfonyl-based solvent. For example, the ethene (=CH2) of ethenesulfonyl fluoride (C2H3SO2F, ESF) can be such an unsaturated organic group.

[0020] Additionally, as mentioned above, some embodiments of the present disclosure include hybrid sulfonyl-based solvent systems comprising a mixture of two or more sulfonyl-based solvents. Synergistic effects using hybrid sulfonyl-based solvent systems have been observed in sulfonyl-based electrolytes using such systems. For example, using a hybrid sulfonyl-based solvent system enables interactions between multiple sulfonyl-based solvents and one or more salts of the electrolyte, and these interactions can result in different and / or novel salt-solvent solvation structures; salt solubility; and physical / chemical / electrochemical properties at both the bulk electrolyte and solid-electrolyte interfaces (compared to conventional solvent systems and / or single sulfonyl-based solvent systems). These different and / or novel aspects of the hybrid sulfonyl-based solvent systems of the present invention can result in superior overall cell performance that cannot be achieved with single-sulfonyl-based solvent systems or conventional solvent systems. Examples of hybrid sulfonyl-based solvent systems include, among others, DSF + ESF and DSF + EMSF.

[0021] In one example, the sulfonyl-based electrolyte of the present invention comprises a lithium bis(fluorosulfonyl)imide (F2LiNO4S2, LiFSI) salt dissolved in a hybrid mixture of ESF and DSF ("hybrid ESF+DS-1" in FIG. 1a and 1b), specifically, 2.0 M LiFSI in (ESF (0.25 mol%) + DSF (99.75 mol%)). As illustrated in FIG. 1a and 1b, this exemplary electrolyte is used in an anode-free pouch cell (Cu / LiNi 0.8 Mn 0.1 Co 0.1 Higher electrochemical stability (Fig. 1a) and CE (Fig. 1b) were achieved in O2 (Cu / NMC811) than in the respective aforementioned single DSF-based electrolytes ("DS": 2.5 M LiFSI of DSF); traditional carbonate-based electrolytes ("FE": 2.5 M LiFSI of fluoroethylene carbonate (FEC) and ethylmethyl carbonate (EMC) in a 3:7 v:v ratio); and optimized ether electrolytes ("DD": 3.97 M LiFSI of 1,4-dioxane (DX) and DEE + 30% 1,2-(1,1,2,2-tetrafluoroethoxy)ethane (TFE) in a 1:5.1 v:v ratio and "DT": 3.6 M LiFSI of ethylene glycol diethyl ether (DEE) + 40% TFE). These cells were circulated at a C / 3-C / 3 rate at room temperature (20°C to 25°C) between 4.3V and 2.5V.

[0022] Referring to FIGS. 2a through 2c, these figures respectively show a lithium-metal anode and LiNi using a sulfonyl-based electrolyte composed of a 2.5 M LiFSI solution in a hybrid sulfonyl-based solvent of ESF (0.25 mol%) / DSF (99.75 mol%) ("Hybrid ESF+DS-2" in FIGS. 2a through 2c) and a sulfonyl-based electrolyte composed of a 3.4 M LiFSI solution in DSF (100 mol%) ("DS"). 0.8 Mn 0.1 Co 0.1The cycling performance of a 0.87 Ah pouch cell containing an O2 (LiNMC811) cathode is illustrated. FIGS. 2a to 2c demonstrate that the hybrid ESF-DSF sulfonyl-based electrolyte of the present invention improves cycling stability better than the DSF electrolyte (Figs. 2a and 2b) and can suppress short circuits in the cell during cycling (Fig. 2c).

[0023] Further examples of hybrid sulfonyl-based solvent systems and corresponding sulfonyl-based electrolytes are based on hybrid mixtures of DSF and EMSF. Figure 3 shows the results of a systematic investigation into the solubility of LiFSI salts in DSF-EMSF-based electrolytes. The electrolytes studied are listed in the table below.

[0024] graph:

[0025]

[0026] As a result of the investigation, each hybrid DSF-EMSF sulfonyl-based electrolyte in the table above unexpectedly demonstrated superior LiFSI salt solubility capability compared to the single-solvent-based electrolyte systems in the table, namely "DS-1" (2.9 M LiFSI with DSF only) and "EM-1" (2.3 M LiFSI with EMSF only). This result suggests that the hybrid sulfonyl-based solvent system of the present invention can significantly improve Li-salt solubility at room temperature without phase separation or salt deposition at 10°C, thereby breaking the Li-salt solubility bottleneck of single-solvent electrolytes (maximum Li-salt solubility in DS-1 and EM-1 is 2.9 M and 2.3 M, respectively) (Fig. 3). This brings significant benefits in the form of improved electrochemical stability. Adding EMSF to DSF can change the solvation energies of the two solvents EMSF and DSF, with Li-salt-LiFSI and coordination ratios of EMSF / DSF and LiFSI. Therefore, this improvement in Li salt solubility is attributed to the synergistic interaction / effect of the hybrid sulfonyl electrolyte rather than the single-solvent electrolyte.

[0027] FIG. 4 shows differential scanning calorimetry (DSC) data for the sulfonyl-based electrolytes of the table above, "hybrid DSF-EMSF-1", "hybrid DSF-EMSF-2", "hybrid DSF-EMSF-3", "hybrid DSF-EMSF-4", "hybrid DSF-EMSF-5", and "hybrid DSF-EMSF-6", as well as the "DS-1" electrolyte of the table above. FIG. 4 shows that there is one distinct peak (400) located at -5°C, which indicates that a phase transition exists in the three electrolytes of "DS-1", "hybrid DSF-EMSF-1" and "hybrid DSF-EMSF-2", and surprisingly, this phase transition peak at -5°C completely disappears when the content of the EMSF solvent component increases to more than 7.5% based on the volume of the hybrid sulfonyl-based solvent system. Another peak (404) located at -30°C to -40°C also gradually shifts to a lower phase transition temperature region as the amount of EMSF solvent in the hybrid sulfonyl-based solvent system increases from 0% to 25% by volume. In the example, FIG. 4 shows that in the sulfonyl-based electrolyte, 7.5% by volume of EMSF solvent in the hybrid sulfonyl-based solvent system is the turning point for this phase transition feature. These results demonstrate that a sulfonyl-based electrolyte having a DSF-EMSF hybrid sulfonyl-based solvent system with more than 7.5% by volume of EMSF significantly improves the low-temperature characteristics of the discovered electrolyte by extending the temperature range of the bottom liquid phase electrolyte. These improved low-temperature characteristics are useful, for example, in battery applications requiring low-temperature operation. These results also confirm that a significant synergy occurs as a result of the competitive coordination / bonding scheme of the salt, DSF, and EMSF, which dominates the chemical and electrochemical properties of the newly discovered sulfonyl-based electrolyte of the present invention.

[0028] The sulfonyl-based solvent system and / or corresponding sulfonyl-based electrolyte of the present invention contains one or more sulfonyl-based solvents having any of the following general chemical structural formulas:

[0029] Structural Formula 1:

[0030] (R1-SO2-R2) [Structural Formula 1]

[0031] In the above structural formula 1,

[0032] R1 and R2 can each be one of the following;

[0033] -F;

[0034] -CF3;

[0035] -N(SO2F)2;

[0036] -N(CH3)SO2F, -N[(CH2) x CH3)][(CH2) y CH3)] (x = 0 to 3, y = 0 to 3);

[0037] -N[(CH2) x CH3][(CH2) y CH=CH(CH2) z -H] (x = 0 to 2; y = 1 to 3, z = 0 to 3);

[0038] -(CH2) x CH=CH(CH2) y -H (x = 0 to 3; y = 0 to 3);

[0039] -C6H 5-x F x (x = 0 to 5);

[0040] -(CH2) x (CH 2-y F y ) z CH 3-w F w (x = 0 to 2, y = 1 to 2, z = 0 to 2, w = 0 to 3);

[0041] -(CH2) x (CH2-y F y ) z F (x = 0 to 2, y = 0 to 2, z = 0 to 2); and

[0042] -(CH2) x CH=CH(CH 2-y F y ) z F (x = 0 to 3, y = 0 to 2, z = 0 to 2); and

[0043] R1≠ R2 or R1= R2.

[0044] Without limitation, the following are exemplary sulfonyl-based solvents having general structural formula 1: 1) R1 is -CH=CH2, R2 is -F, and the solvent is CH2=CHSO2F; 2) R1 is -CH=CH2, R2 is -CF3, and the solvent is CH2=CHSO2CF3; 3) R1 is -N(CH3)2, R2 is -F, and the solvent is (CH3)2NSO2F; 4) R1 is -NCH3SO2F, R2 is F, and the solvent is FSO2N(CH3)SO2F; 5) R1 is -N(CH3)(CH2CH=CH2), R2 is -N(CH3)2, and the solvent is (CH3)(CH2=CHCH2)NSO2N(CH3)2; 6) R1 is -CH=CHCH3, R2 is -N(CH3)(CH2CH3), and the solvent is CH3CH=CHSO2N(CH3)(CH2CH3); 7) R1 is -C6H4F, R2 is -CH2CF3, and the solvent is C6H4FSO2CH2CF3; 8) R1 is -CH2F, R2 is -CH=CHCH2F, and the solvent is FCH2SO2CH=CHCH2F; 9) R1 is -CF2CHCH=CHCH2F, R2 is -N(SO2F)2, and the solvent is CH2FCH=CHCF2SO2N(SO2F)2; 10) R1 is -C6H5, R2 is F, and the solvent is C6H5SO2F; 11) R1 is F, R2 is N(CH3)(CH2CH3), and the solvent is FSO2N(CH3)(CH2CH3); 12) R1 is F, R2 is N(CH2CH3)2, and the solvent is FSO2N(CH2CH3)2; and 13) R1 is CF3, R2 is F, and the solvent is CF3SO2F.

[0045] Example of the structural formula of the aforementioned example of structural formula 1:

[0046] Example 1: Example 11:

[0047]

[0048] Structural formulas 2 and 3:

[0049] (-R3-SO2N-R5SO2-R4-) [Structural Formula 2]

[0050] (-R6-SO2N-(R8)R7-) [Structural Formula 3]

[0051] In the above structural formula,

[0052] R3 is connected annularly to R4, and R6 is connected annularly to R7 by a covalent bond connecting the "-" ends in structural formulas 2 and 3, respectively;

[0053] Each of R3, R4, R6, and R7 can be one of the following.

[0054] -CF2-;

[0055] -CH2-;

[0056] -CH((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1);

[0057] -CF((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1); and

[0058] -CH((CH 2-x F x ) y CH=CH 1-z F z (CH 2-x' F x' ) v H 1-w F w )- (x = 0 to 2, x' = 0 to 2, y = 0 to 2, z = 0 to 1, v = 0 to 2, w = 0 to 1);

[0059] R3≠ R4 or R3= R4;

[0060] R6 ≠ R7 or R6 = R7; and

[0061] R5 and R8 can each be one of the following.

[0062] -(CH2) x CH3(x = 0 to 3); and

[0063] -(CH2) x CH=CH2(x = 1 to 3).

[0064] Without limitation, the following are exemplary sulfonyl-based solvents having general structural formula 2 or general structural formula 3: 1) R3 / R6 is -CH2-, R4 / R7 is -CH2-, R5 / R8 is -CH3, and said solvent is -CH2SO2N(CH3)(SO2CH2-); 2) R3 / R6 is -CF2-, R4 / R7 is -CF2-, R5 / R8 is -CH2CH=CH2, and said solvent is -CF2SO2N(CH2CH=CH2)(CF2)-; 3) R3 / R6 is -CH(CH=CH2F)-, R4 / R7 is -CH(CH=CH2)-, R5 / R8 is -CH3, and said solvent is -(FCH2=CH)CHSO2N(CH3)CH(CH=CH2)-; 4) R3 / R6 is -CH2-, R4 / R7 is -CH2CH2-, R5 / R8 is -CH3, and the solvent is -CH2SO2N(CH3)CH2CH2-; 5) R3 / R6 is -CH2CH2-, R4 / R7 is -CH2CH2-, R5 / R8 is -CH2CH3, and the solvent is -CH2CH2SO2N(CH2CH3)CH2CH2-; and 6) R3 / R6 is -CF2-, R4 / R7 is CF2, R5 / R8 is CH3, and the solvent is -CF2SO2N(CH3)SO2CF2-.

[0065] Example of the structural formula of the aforementioned example of structural formula 2:

[0066] Example 1: Example 2:

[0067]

[0068] Example of the structural formula of the aforementioned example of structural formula 3:

[0069] Example 4: Example 5:

[0070]

[0071] Structural Formula 4:

[0072] (R9-SO2N-(R 10 )(R 11 )) [Structural Formula 4]

[0073] In the above structural formula,

[0074] R9 is -(CH2) x (CH 2-y F y ) z F can be (x = 0 to 2, y = 0 to 2, z = 0 to 2);

[0075] R 10 -(CH2) x O(CH2) y CH3(x = 2 to 4, y = 0 to 2) may be; and

[0076] R 11 -(CH2) x CH3(x = 0 to 3); or -(CH2) x O(CH2) y CH3(x = 2 to 4, y = 0 to 2) may be used.

[0077] Without limitation, the following is an exemplary sulfonyl-based solvent having general structural formula 4: 1) R9 is -F, and R 10 is -(CH2)2OCH3, and R 11 ≡ is -(CH2)2OCH3, and the solvent is FSO2N[(CH2)2OCH3]2; 2) R9 is -F, and R 10 is -(CH2)2OCH3, and R 11 is -CH3, and the solvent is FSO2N[(CH2)2OCH3][CH3]; 3) R9 is -CF3, and R 10 is -(CH2)2OCH3, and R 11≡ is -(CH2)2OCH3, and the solvent is CF3SO2N[(CH2)2OCH3]2; and 4) R9 is -CF3, and R 10 is -(CH2)2OCH3, and R 11 It is -CH3, and the solvent is CF3SO2N[(CH2)2OCH3][CH3].

[0078] Example of the structural formula of the aforementioned example of structural formula 4:

[0079] Example 1: Example 4:

[0080]

[0081] Structural Formula 5:

[0082] (R 12 -SO2-R 13 ) [Structural Formula 5]

[0083] In the above structural formula,

[0084] R 13 Within it, there are ring structures containing N, O, hydrocarbons only, or a mixture of N and O;

[0085] R 12 -(CH2) x (CH 2-y F y ) z F can be (x = 0 to 2, y = 0 to 2, z = 0 to 2);

[0086] R 13 -N(CH2)4(1-pyrrolidino 5-membered ring);

[0087] -N(CH2)5(1-piperidinyl 6-membered ring);

[0088] -N(CH2CH2)2O (4-morpholnyl 6-membered ring);

[0089] -C5H9(cyclopentane);

[0090] -C6H 11 (cyclohexane);

[0091] -C4H7O (2 or 3-tetrahydrofuran); or

[0092] It may be a fluorinated analogue of this.

[0093] Without limitation, the following is an exemplary sulfonyl-based solvent having general structural formula 5:

[0094] 1) R 12 is -F, and R 13 is -N(CH2)4, and the solvent is FSO2N(CH2)4 (5-membered ring); 2) R 12 is -CF3, and R 13 is -N(CH2)4 (5-membered ring), and the solvent is CF3SO2N(CH2)4 (5-membered ring); 3) R 12 is -F, and R 13 The silver is -N(CH2CH2)2O (6-membered ring), and the solvent is FSO2N(CH2CH2)2O (6-membered ring).

[0095] Example of the structural formula of the aforementioned example of structural formula 5:

[0096] Example 2: Example 3:

[0097]

[0098] The sulfonyl-based solvent system and / or the sulfonyl-based electrolyte of the present invention may comprise a single type of sulfonyl-based solvent of the present invention, or a mixture of two or more sulfonyl-based solvents disclosed herein, including both a linear sulfonyl-based solvent and a cyclic sulfonyl-based solvent, wherein each solvent is, for example, in the range of about 100% to about 0.05% by volume, weight, or molar ratio, or in the range of about 5% to about 50% by volume, weight, or molar ratio. Where the sulfonyl-based solvent system or the sulfonyl-based electrolyte comprises only a single solvent, Structural Formula 1 does not include the case where R1 and R2 are either -F or -CF3, and the case where R1 and R2 are -N(CH3)2.

[0099] Additionally, the sulfonyl-based solvent system and electrolyte of the present invention may include one or more solvents other than the sulfonyl-based solvent, or a "non-sulfonyl-based solvent" mixed with the sulfonyl-based solvent. Examples of non-sulfonyl-based solvents that can be used in the sulfonyl-based solvent system and sulfonyl-based electrolyte of the present invention include, for example, cyclic or linear, non-fluorinated or fluorinated carbonates, ethers, nitriles, phosphates, sulfons, sultones, and sulfates in combination with each solvent of the sulfonyl-based solvent system in a range of about 100% to about 0.05% by volume, weight, or molar ratio, or in a range of about 5% to about 50% by volume, weight, or molar ratio, but are not limited thereto.

[0100] In some embodiments, one or more of the following salts may be combined with any one of the newly discovered sulfonyl-based solvent systems to form the sulfonyl-based electrolyte of the present disclosure: LiFSI, LiTFSI, LiClO4, LiBF4, LiPF6, LiAsF6, LiTF, LiBETI, LiCTFSI, LiTDI, LiPDI, LiDCTA, LiB(CN)4, LiBOB, LiDFOB, among others, in concentrations ranging from about 0.1 M to about 5.5 M. It is noted that the exemplary salts described above are lithium-based, but the Li cations of these salts may be replaced, among other things, with other cations such as Na, Mg, K and Zn. In some embodiments, concentrations of the salt(s) in the range of about 0.9 M to about 3.5 M may be preferred. For example, when LiFSI salt and EMSF solvent are selected, an exemplary preferred range is about 2.0 M to about 3.0 M, when LiFSI salt and DSF / EMSF hybrid solvent are selected, an exemplary preferred range is about 2.5 M to about 3.5 M, and when LiFSI salt and DSF / ethylene glycol diethyl ether (DEE) solvent are selected, an example preferred range is about 2.5 M to about 4.5 M. It is noted that although the aforementioned salts are all lithium-based, salts of one or more other alkali metals, such as sodium or potassium, may be used with the sulfonyl-based solvent system of the present invention depending on the chemical properties of the specific sulfonyl-based electrolyte in question. It is also noted that the sulfonyl-based solvent system of the present invention may be suitable for Li-ion cells and batteries. In some examples for Li-ion cells and batteries, the salt-solvent molar ratio may be in the range of about 1:7 to about 1:1. For example, when LiFSI salt and bis(2-methoxyethyl)sulfamoyl fluoride (BMSF) solvent are used, the molar concentration of LiFSI salt may be about 5.5 M per liter of solvent, and the corresponding LiFSI:BMSF molar ratio is about 1:1.

[0101] The advantages of the discovered sulfonyl-based electrolytes disclosed herein may include the following:

[0102] 1) The new sulfonyl-based electrolyte not only has high stability and high Coulomb efficiency for the Li metal anode but can also promote the formation of a robust and protective passivation layer on the Li surface (Fig. 1, the new hybrid sulfonyl-based electrolyte provided a high CE value (99.65%) and long-lasting cycles).

[0103] 2) The disclosed sulfonyl-based electrolyte provides a beneficial synergistic effect that improves the cycling stability of the entire cell during cycling and lowers the DCIR (75% of the DCIR value based on a single DSF-containing electrolyte after 100 cycles) (Fig. 2).

[0104] 3) The disclosed sulfonyl-based electrolyte has good behavior and can have excellent oxidation stability at high voltage over a wide temperature range, so solvent decomposition of the cathode surface at high voltage can be greatly minimized. Figure 5 is a linear scanning potentiometry (LSV) scan plot for a conventional ether-based electrolyte (3.97 M LiFSI in 1,4-dioxane (DX) and DEE at a ratio of 1:5.1 v:v + 30% TFE; "DD") and a sulfonyl-based electrolyte (2.5 M LiFSI in DSF; "DS"). LSV was performed with a platinum electrode at room temperature (~20°C), 45°C, and 60°C. As shown in Figure 5, the "DS" electrolyte exhibited significantly lower oxidation current densities at high temperatures and high voltages compared to the conventional "DD" electrolyte. Furthermore, as seen in the LSV scan plot in Figure 6 (platinum electrode at 30°C), it was demonstrated that the hybrid sulfonyl-based electrolyte of the present invention ("Hybrid DSF-EMSF-5" (see table above)) possesses superior oxidation stability compared to a single DSF-containing electrolyte ("DS-1" (see table above)).

[0105] 4) Both the "DD" and "DS" electrolytes of FIG. 5 also do not have aluminum corrosion problems (see the cyclic voltammetry (CV) plot of FIG. 7 with aluminum electrodes). Surprisingly, the hybrid sulfonyl-based electrolyte of the present invention (hereinafter "hybrid DSF-EMSF-5" (see table above)) can passivate the aluminum electrode surface more rapidly compared to the single DSF "DS-1" electrolyte (see FIG. 8).

[0106] 5) One of the sulfonyl-based electrolytes of the present invention may exhibit good thermal stability and processability due to having a relatively high boiling point (e.g., >150°C).

[0107] 6) One of the sulfonyl-based electrolytes of the present invention may have a relatively low cost because the salt molar concentration is reduced when using the sulfonyl-based solvent system of the present invention, in which at least one of the sulfonyl-based solvents has a molecular weight greater than the molecular weight of DSF.

[0108] 7) One of the sulfonyl-based electrolytes of the present invention may have low or no flammability, which allows for meeting higher safety requirements when considering the highly flammable carbonate-based conventional electrolytes widely used in Li-ion batteries today.

[0109] Embodiments of the present disclosure include the individual sulfonyl-based solvents and sulfonyl-based solvent systems described above, as well as mixtures of these solvents together, including but not limited to the specific mixtures mentioned above. Embodiments of the present disclosure also include any exemplary mixtures and sulfonyl-based electrolytes prepared using any one or more sulfonyl-based solvent systems described above, each comprising one or more salts including the lithium-based salts and / or mixtures thereof listed above, and any salt or mixture thereof based on an alkali metal other than lithium, such as sodium or potassium. Embodiments of the present disclosure further include electrochemical devices, such as batteries and supercapacitors, each comprising an electrolyte prepared according to aspects of the present disclosure. Examples of batteries include LMBs, lithium-ion batteries, and batteries based on alkali metals other than lithium, e.g., sodium metal batteries or potassium metal batteries. Those skilled in the art understand that many different configurations of electrochemical apparatus may utilize an electrolyte prepared according to the present disclosure, and all suitable configurations of such conventional electrochemical apparatus are incorporated herein as a basis for an electrochemical apparatus prepared according to the present invention, comprising an electrochemical apparatus configured in a conventional manner containing a sulfonyl-based electrolyte (and sulfonyl-based solvent(s)) prepared according to the present invention.

[0110] Various modifications and additions may be made without departing from the spirit and scope of the invention. The features of each of the various embodiments described above may be combined with features of other described embodiments suitable for providing a combination of features in a related new embodiment. Furthermore, while the foregoing describes a number of individual embodiments, what is described herein is merely illustrative of the application of the principles of the invention. Additionally, while specific methods of this specification may be illustrated and / or described as being performed in a specific order, the order is highly variable within the art to achieve the aspects of this disclosure. Accordingly, this description is taken merely as an example and does not otherwise limit the scope of the invention.

[0111] Exemplary embodiments are disclosed above and illustrated in the accompanying drawings. Those skilled in the art will understand that various changes, omissions, and additions may be made to what is specifically disclosed herein without departing from the spirit and scope of the invention.

Claims

Claim 1 An electrolyte for an electrochemical device having an alkali metal anode having an anode active material comprising an alkali metal, wherein the electrolyte comprises a sulfonyl-based solvent system comprising one or more sulfonyl-based solvents, and at least one alkali metal salt dissolved in the one or more sulfonyl-based solvents, wherein the alkali metal salt has a cation comprising the alkali metal of the anode active material; wherein each solvent of the sulfonyl-based solvent system has one of the following general molecular structural formulas: Structural Formula 1: R1-SO2-R2, wherein R1 and R2 may each be one of the following: -F; -CF3; -N(SO2F)2; -N(CH3)SO2F, -N[(CH2) x CH3)][(CH2) y CH3)] (x = 0 to 3, y = 0 to 3);-N[(CH2) x CH3][(CH2) y CH=CH(CH2) z -H] (x = 0 to 2; y = 1 to 3, z = 0 to 3);-(CH2) x CH=CH(CH2) y -H (x = 0 to 3; y = 0 to 3);-(CH2) x (CH 2-y F y ) z F (x = 0 to 2, y = 0 to 2, z = 0 to 2); and -(CH2) x CH=CH(CH 2-y F y ) z F (x = 0 to 3, y = 0 to 2, z = 0 to 2); R1 ≠ R2 or R1 = R2, provided that R1 and R2 are simultaneously -(CH2) x CH=CH(CH2) y -H (x = 0 to 3; y = 0 to 3) is not; at least one of R1 and R2 comprises at least one of nitrogen and fluorine; Structural Formula 2: -R3-SO2N-R5SO2-R4-, wherein R3 and R4 may each be one of the following: -CF2-; -CH2-; -CH((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1);-CF((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1); and-CH((CH 2-x F x ) y CH=CH 1-z F z (CH 2-x' F x' ) v H 1-w F w )- (x = 0 to 2, x' = 0 to 2, y = 0 to 2, z = 0 to 1, v = 0 to 2, w = 0 to 1);R3≠ R4 or R3= R4; and R5 may be one of the following;-(CH2) x CH3(x = 0 to 3); and-(CH2) x CH=CH2(x = 1 to 3); Structural Formula 3: -R6-SO2N-(R8)R7-, where R6 and R7 each may be one of the following: -CF2-; -CH2-; -CH((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1);-CF((CH2) x H 1-y F y )- (x = 0 to 3, y = 0 to 1); and-CH((CH 2-x F x ) y CH=CH 1-z F z (CH 2-x' F x' ) v H 1-w F w )- (x = 0 to 2, x' = 0 to 2, y = 0 to 2, z = 0 to 1, v = 0 to 2, w = 0 to 1);R6≠R7 or R6=R7; and R8 may be one of the following;-(CH2) x CH3(x = 0 to 3); and-(CH2) x CH=CH2(x = 1 to 3); Structural Formula 4: R9-SO2N-(R 10 )(R 11 ), in the above structural formula 4, R9 is -(CH2) x (CH 2-y F y ) z F (x = 0 to 2, y = 0 to 2, z = 0 to 2) and; R 10 -(CH2) x O(CH2) y CH3(x = 2 to 4, y = 0 to 2) and R 11 can be one of the following;-(CH2) x CH3(x = 0 to 3); and-(CH2) x O(CH2) y CH3(x = 2 to 4, y = 0 to 2); and structural formula 5: R 12 -SO2-R 13 , in the above structural formula 5, R 13 Within, there are ring structures containing nitrogen (N), oxygen (O), hydrocarbons only, or a mixture of (N+O);R 12 -(CH2) x (CH 2-y F y ) z F (x = 0 to 2, y = 0 to 2, z = 0 to 2) and; R 13 It can be one of the following: -C5H9 (cyclopentane); -C6H 11 (cyclohexane); -C4H7O (2 or 3-tetrahydrofuran); and fluorinated analogs thereof; an electrolyte for an electrochemical device, wherein the electrolyte contains a single solvent and the single solvent has structural formula 1, wherein structural formula 1 does not include the case where R1 and R2 are either -F or -CF3 and is -N(CH3)2. Claim 2 An electrolyte for an electrochemical device according to claim 1, wherein the electrolyte comprises only a single solvent among the sulfonyl-based solvents. Claim 3 An electrolyte for an electrochemical device according to claim 2, wherein a single solvent among the sulfonyl-based solvents has a general molecular structural formula selected from the group consisting of structural formula 2, structural formula 3, structural formula 4, and structural formula 5. Claim 4 An electrolyte for an electrochemical device according to claim 1, wherein the electrolyte comprises two or more sulfonyl-based solvents. Claim 5 An electrolyte for an electrochemical device according to claim 4, wherein the electrolyte further comprises at least one non-sulfonyl-based solvent. Claim 6 An electrolyte for an electrochemical device according to claim 1, wherein at least one of the sulfonyl-based solvents has structural formula 1 and is selected from the group consisting of CH2=CHSO2F; CH2=CHSO2CF3; (CH3)2NSO2F; FSO2N(CH3)SO2F; (CH3)(CH2=CHCH2)NSO2N(CH3)2; CH3CH=CHSO2N(CH3)(CH2CH3); FCH2SO2CH=CHCH2F; CH2FCH=CHCF2SO2N(SO2F)2; FSO2N(CH3)(CH2CH3); FSO2N(CH2CH3)2; and CF3SO2F. Claim 7 An electrolyte for an electrochemical device according to claim 1, wherein at least one of the sulfonyl-based solvents has structural formula 2 or structural formula 3. Claim 8 Electrolyte for an electrochemical device according to claim 7, wherein at least one sulfonyl-based solvent is selected from the group consisting of -CH2SO2N(CH3)(SO2CH2-); -CF2SO2N(CH2CH=CH2)(CF2)-; -(FCH2=CH)CHSO2N(CH3)CH(CH=CH2)-; and -CF2SO2N(CH3)SO2CF2-. Claim 9 An electrolyte for an electrochemical device according to claim 1, wherein at least one of the sulfonyl-based solvents has structural formula 4. Claim 10 An electrolyte for an electrochemical device according to claim 9, wherein at least one of the sulfonyl-based solvents is selected from the group consisting of FSO2N[(CH2)2OCH3]2; FSO2N[(CH2)2OCH3][CH3]; CF3SO2N[(CH2)2OCH3]2; and CF3SO2N[(CH2)2OCH3][CH3]. Claim 11 An electrolyte for an electrochemical device according to claim 1, wherein at least one of the sulfonyl-based solvents has structural formula 5. Claim 12 An electrolyte for an electrochemical device, wherein the electrolyte defines the weight of the electrolyte, and the sulfonyl-based solvent system has a weight percentage of at least 80% of the weight of the electrolyte. Claim 13 Electrolyte for an electrochemical device according to claim 1, wherein the electrochemical device comprises a lithium-metal battery having a lithium-metal anode, and the at least one alkali-metal salt comprises at least one lithium salt. Claim 14 Electrolyte for an electrochemical device according to claim 13, wherein at least one lithium salt is selected from the group consisting of LiFSI, LiTFSI, LiClO4, LiBF4, LiPF6, LiAsF6, LiTF, LiBETI, LiCTFSI, LiTDI, LiPDI, LiDCTA, LiB(CN)4, LiBOB, and LiDFOB. Claim 15 An electrolyte for an electrochemical device according to claim 14, wherein at least one lithium salt is LiFSI and the sulfonyl-based solvent system comprises N-ethyl, N-methyl sulfamoyl fluoride (EMSF). Claim 16 An electrolyte for an electrochemical device according to claim 14, wherein at least one lithium salt is LiFSI, and the sulfonyl-based solvent system comprises N-ethyl, N-methyl sulfamoyl fluoride (EMSF) combined with N,N-dimethylsulfamoyl fluoride (DSF), or a compound in which the amine group of DSF is replaced with a saturated or unsaturated hydrocarbon group, or an EMSF combined with a compound in which at least one methyl group of DSF is replaced with an electron-withdrawing substituent. Claim 17 An electrolyte for an electrochemical device according to claim 16, wherein the saturated or unsaturated hydrocarbon group is an alkyl, alkene, alkyne, or aromatic group, with or without a fluorosubstitute. Claim 18 An electrolyte for an electrochemical device according to claim 16, wherein the electron-withdrawing substituent is a fluoro-substituted alkyl group or an oxyalkyl group. Claim 19 Electrolyte for an electrochemical device according to claim 1, wherein at least one of the sulfonyl-based solvents is selected from the group consisting of N-ethyl, N-methyl sulfamoyl fluoride (EMSF), diethyl sulfamoyl fluoride (DESF), bis(2-methoxyethyl) sulfamoyl fluoride (BMSF) and ethensulfonyl fluoride (ESF). 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