Electrolyte comprising solvent with non-fluorine halogen substitute and batteries comprising same

Abstract

Disclosed is an electrolyte comprising a lithium salt and an organic solvent with a high boiling point, wherein the organic solvent is an ether comprising a non-fluorine halogen substitute. In some embodiments, the organic solvent has a formula of X-CH2-[CH2OCH2]n-CH2Y or Z-CH2-[CH2OCH2]n-CH3-mFm, and each formula comprises at least one selected from Cl, Br, I, and CN, wherein 1 ≤ n ≤15, 1≤ m ≤ 3, X and Y are each independently selected from the group consisting of H, CH3, C2H5, Cl, Br, I, and CN, Z is selected from the group consisting of Cl, Br, I, and CN. In some embodiments, the organic solvent is an ether with a cyclic structure. In one embodiment, the high boiling point is 105 oC or above. The electrolyte and an electrochemical device comprising the same exhibit an improved thermal stability and safety.

Description

ELECTROLYTE COMPRISING SOLVENT WITH NON-FLUORINE HALOGEN SUBSTITUTE AND BATTERIES COMPRISING SAMECROSS-REFERENCE

[0001] This application claims the priority of US Appl. No. 63 / 592,988, filed on October 25, 2023, the entire contents of which is hereby incorporated by reference in its entirety.FIELD

[0002] Disclosed are an electrolyte comprising a lithium salt and an organic solvent comprising non-fluorine halogen substitute and with a boiling point of 105 °C or higher, and an electrochemical device comprising the electrolyte.BACKGROUND

[0003] Fluorinated ether is one of the widely used solvents in electrolytes due to their electrochemical stability, good ion transportation properties and good cycling performance as a result of formation of LiF-rich solid-electrolyte interface (SEI). However, conventional fluorinated ethers such as bis(2,2,2-trifluoroethyl) ether (BTFE) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) have a low boiling point (bp) of 62 °C and 92 °C, respectively. This may lead to a less desirable safety profile, for example, leaking and venting of electrolyte components, thermal runaway, explosion and / or fire, especially when the electrolyte in a battery experiences a high temperature due to self-heating or external heating. The safety risks will be even higher if the battery comprises a Li metal anode. Thus, there remains a need for electrolytes with improved battery safety.SUMMARY

[0004] The present disclosure provides an electrolyte comprising a lithium salt and an organic solvent with a high boiling point, wherein the organic solvent comprises a halogen substitute which is not fluorine. In some embodiments, the organic solvent is an ether comprising a non- fluorine halogen substitute. In some embodiments, the organic solvent has a formula of X-CH2- [CH2OCH2]n-CH2Y wherein 1 < n <15, X and Y are each independently selected from thegroup consisting of H, CH3, C2H5, Cl, Br, I, and CN, and the formula comprises at least one selected from the group consisting of Cl, Br, I, and CN. In some embodiments, the organic solvent has a formula of Z-CH2-[CH2OCH2]n-CH3-mFm, wherein 1 <n <15, I< m < 3, and Z is selected from the group consisting of Cl, Br, I, and CN. In some embodiments, the organic solvent is an ether with a cyclic structure.

[0005] In some embodiments, the organic solvent is a non-ionic chemical.

[0006] In some embodiments, the organic solvent has a linear structure. In some embodiments, the organic solvent has a cyclic structure. In some embodiments, the cyclic organic solvent comprises at least one selected from the group consisting of 2-(chloromethyl)tetrahydrofuran, 2-(bromomethyl)tetrahydrofuran, 2-(iodomethyl)tetrahydrofuran, 3-(chloromethyl)oxolane, 3- (bromomethyl)oxolane, 3-(iodomethyl)oxolane, 2-chlorom ethyl- 1,3 -di oxolane, 4- chloromethyl-l,3-di oxolane, 2-bromom ethyl- 1,3 -di oxolane, 4-bromomethyl-l,3-dioxolane, and mixtures thereof.

[0007] In some embodiments, the organic solvent has a boiling point of at least 105 °C. In some embodiments, the organic solvent comprises bis(2-chloroethyl) ether. In some embodiments, the lithium salt is lithium bis(fluorosulfonyl) imide (LiFSI). In one aspect, an electrochemical device, such as a lithium metal battery, comprising the electrolyte is also disclosed. In one embodiment, the battery exhibits an improved safety profile. Methods for preparing the electrolyte and the lithium metal battery are also disclosed.BRIEF DESCRIPTION OF THE FIGURES

[0008] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shownwhere illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure.

[0009] Fig. 1 shows the cycling performance of Li / Cu cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte according to one embodiment of the present disclosure.

[0010] Fig. 2 shows the cycling performance of Li / Cu cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte according to one embodiment of the present disclosure.

[0011] Fig. 3 shows the cycling performance of Li / Cu cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte according to one embodiment of the present disclosure.

[0012] Fig. 4 shows the cycling performance of Li / Li symmetric cell comprising Li metal as anode, microporous membrane as separator, another Li metal as cathode, and an electrolyte according to one embodiment of the present disclosure.

[0013] Fig. 5 shows the differential scanning calorimetry (DSC) measurement of electrolyte according to one embodiment of the present disclosure.

[0014] Fig. 6 shows the DSC measurement of electrolyte according to one embodiment of the present disclosure.

[0015] Fig. 7 shows the cycling performance of Li / Cu cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte according to one embodiment of the present disclosure.

[0016] Fig. 8 shows a battery comprises cathode (1), anode (2), electrolyte (3) and separator (4).DETAILED DESCRIPTION

[0017] Disclosed is an electrolyte comprising an electrolyte salt (e.g., lithium salt) and an organic solvent comprising a non-fluorine halogen substitute and with a high boilingtemperature. In some embodiments, the organic solvent is an ether comprising a non-fluorine halogen substitute. In some embodiments, the organic solvent has a formula of X-CH2- [CH2OCH2]n-CH2Y, wherein 1 < n <15, X and Y are each independently selected from the group consisting of H, CH3, C2H5, Cl, Br, I, and CN, and wherein the formula comprises at least one selected from the group consisting of Cl, Br, I, and CN. In some embodiments, the organic solvent has a boiling point of at least 105 °C. In some embodiments, the electrolyte and an electrochemical device comprising the same exhibit an improved cycle performance, thermal stability, and safety, for example having suitable values for one or more of the following: ionic conductivity (IC), average Coulombic efficiency (CE), total energy release, and / or EUCAR (European Council for Automotive Research) hazard level after a safety test.

[0018] The electrolytes disclosed herein include a non-fluorine halogen substitute. As used herein, “halogen” refers to elements in group 17 of the periodic table such as fluorine (F), chlorine (Cl), bromine (Br), and Iodine (I) as well as pseudohalogens such as cyanides (CN). As used herein, “pseudohalogens” are polyatomic analogues of halogens with chemistry resembling halogens and allow them to substitute for halogen in a chemical compound. In some embodiments, the electrolyte includes a non-fluorine halogen substitute including, but not limited to Cl, Br, I, or CN.

[0019] In some embodiments, the organic solvent has at least one non-fluorine halogen substitute and has a formula of X-CEE-fCEEOCEEJn-CEbY, wherein 1 < n <15, X and Y are each independently selected from the group consisting of H, CH3, C2H5, Cl, Br, I, and CN, and wherein the formula comprises at least one selected from the group consisting of Cl, Br, I, and CN. In some embodiments, the organic solvent includes two non-fluorine halogen substitutes and X and Y are each independently selected from the group consisting of Cl, Br, I, and CN.

[0020] In some embodiments, the organic solvent includes a fluorine substitute and a non- fluorine halogen substitute and has a formula of Z-CEE-fCEEOCEEln-CEE-mFm, wherein 1 < n <15, 1< m < 3, and Z is selected from the group consisting of Cl, Br, I, and CN. In someembodiments, the organic solvent includes l-chloro-2-(2-fluoroethoxy)ethane, 2-(2- chloroethoxy)- 1 , 1 -difluoroethane, 2-(2-chloroethoxy)- 1,1,1 -trifluoroethane, 1 -bromo-2-(2- fluoroethoxy)ethane, 2-(2 -bromoethoxy)- 1 , 1 -difluoroethane, 2-(2 -bromoethoxy)- 1,1,1- trifluoroethane, l-iodo-2-(2-fluoroethoxy)ethane, 2-(2-iodoethoxy)- 1,1 -difluoroethane, 2-(2- iodoethoxy)-l , 1 , 1 -trifluoroethane, 1 -chloro-2-[2-(2-fluoroethoxy)ethoxy]ethane, 2-[2-(2- chloroethoxy)ethoxy]- 1 , 1 -difluoroethane, 2-[2-(2-chloroethoxy)ethoxy]- 1 ,1,1 -trifluoroethane, 1 -bromo-2-[2-(2-fluoroethoxy)ethoxy] ethane, 2-[2-(2-bromoethoxy)ethoxy]- 1,1- difluoroethane, 2-[2-(2-bromoethoxy)ethoxy]- 1,1,1 -trifluoroethane, 1 -iodo-2-[2-(2- fluoroethoxy)ethoxy] ethane, 2-[2-(2-iodoethoxy)ethoxy]- 1,1 -difluoroethane, and 2-[2-(2- iodoethoxy)ethoxy]- 1,1,1 -trifluoroethane.

[0021] In some embodiments, the organic solvent has a cyclic structure. In some embodiments, the cyclic organic solvent includes at least one selected from the group consisting of 2- (chloromethyl)tetrahydrofuran, 2-(bromomethyl)tetrahydrofuran, 2-(iodomethyl)tetrahydrofuran, 3-(chloromethyl)oxolane, 3-(bromomethyl)oxolane, 3- (iodomethyl)oxolane, 2-chlorom ethyl- 1,3 -di oxolane, 4-chlorom ethyl- 1,3 -di oxolane, 2- bromomethyl-l,3-dioxolane, 4-bromomethyl-l,3-dioxolane, and mixtures thereof.

[0022] In some embodiments, the organic solvent is not an inorganic or organic salt or an ionic liquid. In some embodiments, the organic solvent does not have an ionic structure. In some embodiments, the electrolyte does not comprise water.

[0023] In some embodiments, the organic solvent is a high boiling point solvent with a boiling point of at least 105 °C, at least 110 °C, at least 120 °C, at least 130 °C, at least 140 °C, at least 150 °C, at least 160 °C, at least 170 °C or at least 180 °C. The boiling point is measured at 760 mm Hg unless otherwise specified. In some embodiments, non-limiting specific organic solvents with a high boiling point (bp) greater than or equal to 105 °C include, but is not limited to, bis(2-chloroethyl) ether, bis(2-bromoethyl) ether, l,2-bis(2-chloroethoxy)ethane, l,2-bis(2-bromoethoxy)ethane, butyl 2-chloroethyl ether, butyl 2-bromoethyl ether, 3- ethoxypropionitrile, and mixtures thereof.

[0024] In some embodiments, the electrolyte comprises an organic solvent with a concentration in a range from 10 wt% to 95 wt%, from 10 wt% to 90 wt%, from 10 wt% to 80 wt%, from 10 wt% to 70 wt%, from 10 wt% to 60 wt%, from 10 wt% to 50 wt%, from 10 wt% to 40 wt%, from 10 wt% to 30 wt%, from 10 wt% to 20 wt%, from 20 wt% to 95 wt%, from 20 wt% to 90 wt%, from 20 wt% to 80 wt%, from 20 wt% to 70 wt%, from 20 wt% to 60 wt%, from 20 wt% to 50 wt%, from 20 wt% to 40 wt%, from 20 wt% to 30 wt%, from 30 wt% to 95 wt%, from 30 wt% to 90 wt%, from 30 wt% to 80 wt%, from 30 wt% to 70 wt%, from 30 wt% to 60 wt%, from 30 wt% to 50 wt%, from 30 wt% to 40 wt%, from 30 wt% to 35 wt%, or any and all ranges and subranges therebetween.

[0025] In some embodiments, the electrolyte further includes a second organic solvent with a high boiling point (greater than or equal to 105 °C). In some embodiments, the second organic solvent is ether, fluorinated ether, ionic liquid, ester, carbonate, phosphate, sulfone, or mixtures thereof. In some embodiments, the fluorinated ether is selected from the group consisting of bis(2,2,2-trifluoroethoxy)methane (BTFM), lH,lH,5H-octafluoropentyl 1, 1,2,2- tetrafluoroethyl ether (OTE), and tris(2,2,2-trifluoroethyl)orthoformate (TFEO). In some embodiments, the electrolyte contains a fluorinated ether with a weight percentage in a range from 1 wt% to 40 wt%.

[0026] In some embodiments, the electrolyte further includes an ionic liquid. In some embodiments, the ionic liquid is an imidazolium ionic liquid, a cyclic quaternary ammonium ionic liquid, a phosphonium ionic liquid, a sulfonium ionic liquid, or mixtures thereof.

[0027] In some embodiments, the ionic liquid has a formula ofwherein Ri, R2, R3 are independently selected from the group consisting of hydrogen, Ci-18 alkyl, Ci- is haloalkyl, Ci-18 hydroxyalkyl, Ci-18 aminoalkyl, C2-18 alkenyl, C2-18 alkynyl, and Ce-18 aryl, n is an integer having a value in a range from 1 to 6, R4 and Rs are independently selected from the group consisting of Ci-18 alkyl, Ci-18 haloalkyl, Ci-18 hydroxyalkyl, Ci-18 aminoalkyl,C2-18 alkenyl, C2-18 alkynyl, and Ce-18 aryl, and X' is an anion. Nonlimiting specific Ci-18 alkyls include methyl (-CH3), ethyl (-CH2CH3), i-propyl (-CH(CH3)2), n-propyl (-CH2CH2CH3), n- butyl (-CH2[CH2]2CH3), i-butyl (-CH2CH(CH3)2), n-pentyl (-CH2[CH2]3CH3), n-hexyl (-CH2[CH2]4CH3), n-heptyl (-CH2[CH2]sCH3), n-octyl (-CH2[CH2]6CH3), n-nonyl (-CH2[CH2]7CH3), n-decyl (-CH2[CH2]8CH3), n-undecyl (-CH2[CH2]9CH3), n-dodecyl (-CH2[CH2]IOCH3), n-tridecyl (-CH2[CH2]nCH3), n-tetradecyl (-CH2[CH2]i2CH3), n-hexadecyl(-CH2[CH2] 14CH3), n-octadecyl (-CEbfCEblieCEE), and any combination thereof.

[0028] In some embodiments, the anion X' is selected from the group consisting of bis(fluorosulfonyl)imide (FSF), bis(trifluoromethanesulfonyl)imide (TFSF), hexafluorophosphate (PFe‘), tetrafluoroborate (BF4‘), bis(oxalate)borate (BOB'), difluoro(oxalato)borate (DFOB'), trifluoromethanesulfonate (TfO‘), nitrate (NO3 ), dicyanamide (DC A'), fluoride (F‘), chloride (CF), bromide (Br ), and mixtures thereof.

[0029] In some embodiments, the ionic liquid is selected from the group consisting of 1-ethyl- 3 -methylimidazolium bis(fluorosulfonyl) imide (EmimFSI), l-butyl-3 -methylimidazolium bis(fluorosulfonyl) imide (BmimFSI), l-hexyl-3-methylimidazolium bis(fluorosulfonyl) imide (HmimFSI), 1 -vinyl-3 -methylimidazolium bis(fluorosulfonyl) imide (VmimFSI), l-ethyl-3- methylimidazolium bi s(tri fluoromethanesulfonyl) imide (EmimTFSI), l-butyl-3- methylimidazolium bi s(tri fluoromethanesulfonyl) imide (BmimTFSI), l-hexyl-3- methylimidazolium bi s(tri fluoromethanesulfonyl) imide (HmimTFSI), 1 -vinyl-3 - methylimidazolium bis(tri fluoromethanesulfonyl) imide (VmimTFSI), N-propyl-N- methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI), 1 -butyl- 1 -methylpyrrolidiniumbis(fluorosulfonyl)imide (PYR14FSI), 1 -butyl- 1-methylpyrrolidinium bis(oxalate)borate (PYR14B0B), 1 -butyl- 1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide(PYR14TFSI), 1 -butyl- 1-methylpyrrolidinium di cyanamide (PYR14DCA), 1 -butyl- 1- methylpyrrolidinium trifluoromethanesulfonate (PYR14TfO), 1 -methyl- 1 -(2- methoxyethyl)pyrrolidinium bis(fluorosulfonyl)imide (PYOFSI), 1-methyl-l- pentylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR15TFSI), 1-methyl-l- octylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR18TFSI), N-propyl-N- methylpiperidinium bis(fluorosulfonyl)imide, N-propyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1-methylpiperidinium bis(fluorosulfonyl)imide, 1 -butyl- 1 -methylpiperidinium bis(oxalate)borate, 1 -butyl- 1 -methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1-methylpiperidinium dicyanamide, 1-butyl-l- methylpiperidinium trifluoromethanesulfonate, 1 -methyl- 1 -(2 -m ethoxy ethyl)piperidinium bis(fluorosulfonyl)imide, 1 -methyl- 1-pentylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -methyl- 1-octylpiperidinium bis(trifluoromethanesulfonyl)imide, N-propyl-N- methylazepanium bis(fluorosulfonyl)imide, N-propyl-N-methylazepanium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1-methylazepanium bis(fluorosulfonyl)imide, 1- butyl- 1 -methylazepanium bis(oxalate)borate, 1 -butyl- 1 -methylazepanium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1 -methyl azepanium dicyanamide, 1-butyl-l- methylazepanium trifluoromethanesulfonate, 1 -methyl- 1 -(2-methoxyethyl)azepanium bis(fluorosulfonyl)imide, 1 -methyl- 1-pentylazepanium bis(trifluoromethanesulfonyl)imide, 1- methyl-l-octylazepanium bis(trifluoromethanesulfonyl)imide, and mixtures thereof.

[0030] In some embodiments, the electrolyte includes an ionic liquid with a weight percentage in a range from 10 wt% to 80 wt%, from 10 wt% to 70 wt%, from 10 wt% to 60 wt%, from 10 wt% to 50 wt%, from 10 wt% to 40 wt%, from 10 wt% to 30 wt%, from 20 wt% to 80 wt%, from 20 wt% to 70 wt%, from 20 wt% to 60 wt%, from 20 wt% to 50 wt%, from 20 wt% to 40 wt%, from 20 wt% to 30 wt%, from 30 wt% to 80 wt%, from 30 wt% to 70 wt%, from 30 wt%to 60 wt%, from 30 wt% to 50 wt%, from 30 wt% to 40 wt%, from 35 wt% to 80 wt%, from35 wt% to 70wt%, from 35 wt% to 60 wt%, from 35 wt% to 50 wt%, from 35 wt% to 40 wt%, from 40 wt% to 80 wt%, from 40 wt% to 70 wt%, from 40 wt% to 60 wt%, from 40 wt% to 50 wt%, or any and all ranges and subranges therebetween.

[0031] In some embodiments, the electrolyte salt may include one or more lithium salts. In one embodiment, the lithium salts are selected from the group consisting of lithium bis(fluorosulfonyl) imide (LiFSI), lithium perchlorate (LiCICh), lithium hexafluorophosphate (LiPFe), lithium borofluoride (LiBF4), lithium hexafluoroarsenide (LiAsFe), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SCh)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium nitrate (LiNCh), lithium fluoroalkylphosphates (Li[PFx(CyF2y+i-zHz)6-x]) (l<x<5, l<y<8, and 0<z<2y-l), lithium bis(perfluoroethanesulfonyl)imide (LiBETI), lithium difluoro(oxalato)borate (LiDFOB), lithium fluorophosphate (Li2PO3F), lithium difluoro(bisoxalato)phosphate (LiC4PO8F2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium difluorophosphate (LiDFP), LiC(CF3SO2)3, LiF, LiCl, LiBr, Lil, Li2SO4, LisPCh, Li2CO3, lithium acetate, lithium trifluoromethyl acetate, lithium oxalate, and mixtures thereof.

[0032] In some embodiments, the electrolyte includes a lithium salt with a concentration in a range from 10 wt% to 60 wt%, from 10 wt% to 50 wt%, from 10 wt% to 40 wt%, from 10 wt% to 30 wt%, , from 10 wt% to 20 wt%, from 12.5 wt% to 60 wt%, from 15 wt% to 60 wt%, from 15 wt% to 50 wt%, from 15 wt% to 40 wt%, from 15 wt% to 30 wt%, from 15 wt% to 20 wt%, from 20 wt% to 60 wt%, from 20 wt% to 50 wt%, from 20 wt% to 40 wt%, from 20 wt% to 30 wt%, from 20 wt% to 25 wt%, or any and all ranges and subranges therebetween.

[0033] In some embodiments, the electrolyte further includes a polymer to improve the thermal stability and / or safety. In some embodiments, the polymer is added into a mixture containing a lithium salt, and an organic solvent comprising a non-fluorine halogen substitute. In some embodiments, the organic solvent is an ether comprising a non-fluorine halogen substitute.

[0034] In some embodiments, the electrolyte includes a polymer with a concentration in a range from 0.02 wt% to 40.0 wt%, from 0.02 wt% to 30.0 wt%, from 0.02 wt% to 20.0 wt%, from 0.02 wt% to 15.0 wt%, from 0.02 wt% to 10.0 wt%, from 0.02 wt% to 5.0 wt%, from 0.02 wt% to 1.0 wt%, from 0.02 wt% to 0.5 wt%, from 0.05 wt% to 40.0 wt%, from 0.05 wt% to 30.0 wt%, from 0.05 wt% to 20.0 wt%, from 0.05 wt% to 15.0 wt%, from 0.05 wt% to 10.0 wt%, from 0.05 wt% to 5.0 wt%, from 0.05 wt% to 1.0 wt%, from 0.05 wt% to 0.5 wt%, from 0.1 wt% to 40.0 wt%, from 0.1 wt% to 30.0 wt%, from 0.1 wt% to 20.0 wt%, from 0.1 wt% to 15.0 wt%, from 0.1 wt% to 10.0 wt%, from 0.1 wt% to 5.0 wt%, from 0.1 wt% to 1.0 wt%, from 0.1 wt% to 0.5 wt%, from 0.5 wt% to 40.0 wt%, from 0.5 wt% to 30.0 wt%, from 0.5 wt% to 20.0 wt%, from 0.5 wt% to 15.0 wt%, from 0.5 wt% to 10.0 wt%, from 0.5 wt% to 5.0 wt%, from 0.5 wt% to 1.0 wt% or any and all ranges and subranges therebetween.

[0035] In some embodiments, the polymer is in situ polymerized after a polymerizable monomer and initiator is mixed with a lithium salt, and an organic solvent with a non-fluorine halogen substitute. When an electrolyte comprises a polymer, the electrolyte is referred to as polymer electrolyte.

[0036] In some embodiments, the polymer electrolyte is prepared by an in situ polymerization in the presence of an initiator such as azobisisobutyronitrile (AIBN), ammonium persulfate (APS), potassium persulfate (PPS), sodium persulfate (SPS), and lithium persulfate (LPS). In some embodiments, the polymer electrolyte is prepared by an in situ polymerization in the presence of an initiator that does not generate gas during the polymerization. Such a non-gas generating initiator is an initiator that does not have any groups leading to gas formation during the polymerization.

[0037] In some embodiments, the initiator is a persulfate. In some embodiments, a persulfate initiator comprises an anion of SOs2-, SiO;or both. In some embodiments, non-limiting specific persulfate initiators include ammonium persulfate (APS), potassium persulfate (PPS), sodium persulfate (SPS), lithium persulfate (LPS) and any combination thereof. In someembodiments, the electrolyte composition does not include gas generating initiators, such as azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO).

[0038] In some embodiments, the mixture prior to in situ polymerization contains an initiator in an amount from 0.001 wt% to 10 wt%. In some embodiments, the mixture contains an initiator in an amount from 0.002 wt% to 10 wt%, from 0.005 wt% to 10 wt%, from 0.01 wt% to 10 wt%, from 0.02 wt% to 10 wt%, from 0.05 wt% to 10 wt%, from 0.1 wt% to 10 wt%, from 0.2 wt% to 10 wt%, from 0.5 wt% to 10 wt%, from 1.0 wt% to 10 wt%, from 2.0 wt% to 10 wt% or any and all ranges and subranges therebetween.

[0039] In some embodiments, the monomer contains one or more polymerizable groups. In some embodiments, non-limiting specific polymerizable groups include vinyl (-CH=CH2), substituted vinyl (-CRI=CR2R3) and a combination thereof, wherein Rl, R2 and R3 are independently hydrogen, halogen, -CN, -NO2, C1-6 alkyl, Ci-ehaloalkyl, Ci-ehydroxyalkyl, C1-6 aminoalkyl, C2-6 alkenyl, C2-6 alkynyl, Ce-14 aryl or any combination thereof. Non-limiting specific monomers include 2,2,3,3-tetrafluorobutane-l,4-diacrylate, 2, 2, 3, 3, 4, 4,5,5- octafluorohexane-l,6-diyl diacrylate, 2,2,3,3,4,4,5,5-octafluorohexane-l,6-diyl bis(2- methylacrylate), poly(ethylene glycol) diacrylate (Mn = 500 - 5000), triethylene glycol dimethacrylate (TEGDMA), diurethane dimethacrylate, and any combination thereof.

[0040] In some embodiments, non-limiting monomers are one or more selected from tetraallyl silane (TAS), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, triethoxyvinylsilane, allyltriethoxysilane, pentaerythritol tetraacrylate (PETA), pentaerythritol tetramethacrylate (PETMA), tris[2-(acryloyloxy)ethyl] isocyanurate (TAEI), di(trimethylolpropane) tetraacrylate (Di-TMPTA), trimethylolpropane propoxylate triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0041] In some embodiments, the polymer electrolyte is prepared from a mixture containing multiple monomers.

[0042] In some embodiments, the monomer is mixed with a lithium salt and an organic solvent having a non-fluorine halogen substitute and a high boiling point to form a mixture. In some embodiments, the mixture contains the monomer with a concentration in a range from 0.02 wt% to 40.0 wt%, from 0.02 wt% to 30.0 wt%, from 0.02 wt% to 20.0 wt%, from 0.02 wt% to 15.0 wt%, from 0.02 wt% to 10.0 wt%, from 0.02 wt% to 5.0 wt%, from 0.02 wt% to 1.0 wt%, from 0.02 wt% to 0.5 wt%, from 0.05 wt% to 40.0 wt%, from 0.05 wt% to 30.0 wt%, from 0.05 wt% to 20.0 wt%, from 0.05 wt% to 15.0 wt%, from 0.05 wt% to 10.0 wt%, from 0.05 wt% to 5.0 wt%, from 0.05 wt% to 1.0 wt%, from 0.05 wt% to 0.5 wt%, from 0.1 wt% to 40.0 wt%, from 0.1 wt% to 30.0 wt%, from 0.1 wt% to 20.0 wt%, from 0.1 wt% to 15.0 wt%, from 0.1 wt% to 10.0 wt%, from 0.1 wt% to 5.0 wt%, from 0.1 wt% to 1.0 wt%, from 0.1 wt% to 0.5 wt%, from 0.5 wt% to 40.0 wt%, from 0.5 wt% to 30.0 wt%, from 0.5 wt% to 20.0 wt%, from 0.5 wt% to 15.0 wt%, from 0.5 wt% to 10.0 wt%, from 0.5 wt% to 5.0 wt%, from 0.5 wt% to 1.0 wt% or any and all ranges and subranges therebetween.

[0043] In some embodiments, the electrolyte comprises 25 wt% to 50 wt% lithium salt, and 50 wt% to 75 wt% solvent in the absence of ionic liquid. In some embodiments, the solvent is a mixture comprising at least one solvent with a high boiling point (105°C or higher). In some embodiments, the electrolyte comprises 10 wt% to 45 wt% lithium salt, 10 wt% to 55 wt% solvent, and 20 wt% to 60 wt% ionic liquid. In some embodiments, the lithium salt and the ionic liquid have the same anion to minimize ion exchange.

[0044] In some embodiments, the electrolyte as disclosed herein exhibits a good ionic conductivity (IC). In some embodiments, the electrolyte as disclosed herein exhibits an IC of 1.0 mS / cm or higher, 2.0 mS / cm or higher, 2.5 mS / cm or higher, 3.0 mS / cm or higher, 3.5 mS / cm or higher, 4.0 mS / cm or higher, 4.5 mS / cm or higher, 5.0 mS / cm or higher, 5.5 mS / cm or higher, 6.0 mS / cm or higher, 6.5 mS / cm or higher, or 7.0 mS / cm or higher at room temperature.

[0045] In some embodiments, the electrolyte as disclosed herein exhibits an improved thermal stability in comparison to the one comprising a solvent with a boiling point of less than 105 °C. In one embodiment, the electrolyte as disclosed herein does not exhibit any exothermic or endothermic peak in a differential scanning calorimetry (DSC) curve in a range from room temperature to 110 °C (excluding the peak at the beginning of DSC scanning caused by the DSC system coming to equilibrium). In one embodiment, the electrolyte as disclosed herein does not exhibit any exothermic or endothermic peak in a DSC curve in a range from room temperature to 105 °C. Whether a reversible peak is exothermic or endothermic depends on the scanning direction.

[0046] In some embodiments, the electrolyte does not include any solvent that has a boiling point less than 100 °C, less than 105 °C, less than 110 °C, or less than 120 °C.

[0047] In one aspect, the present disclosure provides an electrochemical device such as lithium metal battery comprising the electrolyte disclosed herein. In some embodiments, a battery comprises cathode (1), anode (2), electrolyte (3) and separator (4) as shown in Fig. 8. The cathode (1) comprises a cathode current collector (10) and a cathode active layer (11). The anode (2) comprises an anode current collector (20) and an anode active layer (21). The electrolyte (3) is located between the separator (4) and either electrode, i.e., either the cathode (1) or the anode (2). In some embodiments, the battery also comprises an anode comprising lithium metal or lithium alloy.

[0048] In some embodiments, an electrochemical device comprising the electrolyte exhibits an improved cycling performance. In some embodiments, the electrochemical device comprising an electrolyte disclosed herein has an average CE of no less 98.00%, no less than 98.25%, no less than 98.50%, no less than 98.75%, no less than 99.00%, no less than 99.10%, no less than99.15%, no less than 99.20%, no less than 99.25%, no less than 99.30%, or no less than 99.35%.

[0049] In some embodiments, an electrochemical device comprises an electrolyte with a good IC (1.0 mS / cm or higher, 2.0 mS / cm or higher, 2.5 mS / cm or higher, 3.0 mS / cm or higher, 3.5mS / cm or higher, 4.0 mS / cm or higher, 4.5 mS / cm or higher, 5.0 mS / cm or higher, 5.5 mS / cm or higher, 6.0 mS / cm or higher, 6.5 mS / cm or higher, or 7.0 mS / cm or higher at room temperature) and simultaneously exhibits a desirable average CE, which can be no less 98.00%, no less than 98.25%, no less than 98.50%, no less than 98.75%, no less than 99.00%, no less than 99.10%, no less than 99.15%, no less than 99.20%, no less than 99.25%, no less than 99.30%, or no less than 99.35%.Table 1 European Council for Automotive Research Hazard Levels

[0050] In one embodiment, an electrochemical device comprising the electrolyte as disclosed herein exhibits an improved thermal stability and safety. Out of many ways, battery safety can be characterized by a hot box test. In general, a fully charged electrochemical device (100% state-of-charge) is placed into an oven in which the temperature of the electrochemical device such as a cell is heated from room temperature to a desired high temperature (such as 190 °C) at a rate of 5 °C / minute and with a holding of 10 min at each of the following temperatures: 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, and 190 °C.

[0051] In some embodiments, after the hotbox test, the electrochemical device does not experience electrolyte leakage, weight loss, explosion, and / or has a European Council for Automotive Research (EUCAR) hazard level of 4 or below or 3 or below. The EUCAR hazard level is shown in Table 1.

[0052] In some embodiments, after the hot box test, the electrochemical device undergoes a weight loss of 40 wt% or less, 45 wt% or less, or less than 50 wt%, based on the total weight of electrolyte in the electrochemical device.

[0053] In some embodiments, the electrochemical device is a coin cell, a pouch cell, or a prismatic cell. In another aspect, the present disclosure provides a method for preparing an electrochemical device comprising an electrolyte with an organic solvent with a boiling point of 105 °C or higher. In some embodiments, the organic solvent is an ether comprising a nonfluorine halogen substitute. In some embodiments, all components in the electrolyte including all solvents have a boiling point of 105 °C or higher. In some embodiments, the electrochemical device comprises an anode layer, a separator, and a cathode layer. In some embodiments, the method comprises: mixing lithium salt, ionic liquid, and the solvent with a bp of 105 °C or higher into an electrolyte.

[0054] In some embodiments, the disclosure provides a method for preparing an electrochemical device comprising an anode layer, a separator, a cathode layer, and an electrolyte as disclosed herein. In one embodiment, the method may comprise:1) mixing a lithium salt, and an organic solvent comprising a non-fluorine halogen substitute and with a high boiling point into an electrolyte;2) placing the anode layer, the separator, and the cathode layer into an assembly;3) injecting the electrolyte into the assembly, thus forming an electrochemical device comprising the anode layer, the separator, the cathode layer and the electrolyte.

[0055] In some embodiments, the organic solvent is an ether comprising a non-fluorine halogen substitute. In some embodiments, the organic solvent has a formula of X-CEb-fCEEOCEb n-CEEY, 1 < n <15, wherein X and Y are each independently selected from the group consisting of H, CH3, C2H5, Cl, Br, I, and CN, wherein the formula comprises at least one selected from Cl, Br, I, and CN.

[0056] In some embodiments, the organic solvent has a formula of Z-CH2-[CH2OCH2]n-CH3-mFm, wherein 1 < n <15, 1< m < 3, and Z is selected from the group consisting of Cl, Br, I, and CN. In some embodiments, the organic solvent is an ether with a cyclic structure and includes a non-fluorine halogen substitute. In some embodiments, the non-fluorine halogen substitute is located on either the ring, a side chain attached to the ring, or both.

[0057] In some embodiments, the disclosure provides a method for preparing an electrochemical device comprising an anode layer, a separator, a cathode layer, and an electrolyte as disclosed herein. In one embodiment, the method may comprise:1) mixing a lithium salt, and a cyclic organic solvent comprising a non-fluorine halogen substitute and with a high boiling point into an electrolyte, wherein the organic solvent is selected from the group consisting of 2-(chloromethyl)tetrahydrofuran, 2- bromomethyl)tetrahydrofuran, 2-(iodomethyl)tetrahydrofuran, 3 -(chloromethyl)oxolane, 3-(bromomethyl)oxolane, 3-(iodomethyl)oxolane, 2-chlorom ethyl- 1,3 -di oxolane, 4- chloromethyl-l,3-dioxolane, 2-bromom ethyl- 1,3 -di oxolane, 4-bromomethyl-l,3- di oxolane, and mixtures thereof;2) placing the anode layer, the separator, and the cathode layer into an assembly;3) injecting the electrolyte into the assembly, thus forming an electrochemical device comprising the anode layer, the separator, the cathode layer and the electrolyte.

[0058] The disclosure will be better understood by reference to the Experimental Details which follow, but those skilled in the art will readily appreciate that the specific experiments detailed are only illustrative, and are not meant to limit the disclosure as described herein, as numerous variations and modifications of these exemplary embodiments are possible without undue experimentation. All such variations and modifications are within the scope of the teachings ofthis disclosure. It will be appreciated that the foregoing description and following examples, no matter how detailed they may appear in text, the disclosure may be practiced in many ways, and the disclosure should be construed in accordance with the appended claims and equivalents thereof.EXAMPLE 1

[0059] Li stripping / plating Coulombic efficiency (CE) is a critical parameter for the evaluation of electrolyte stability on Li metal anode. The Li stripping / plating CE was obtained by stripping / plating cycles in Li / Cu cells comprising Li metal as anode, Cu foil as cathode, microporous membrane as a separator, and an electrolyte with a composition in Table 2 prepared by mixing the lithium salt, l-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EmimFSI), and l,2-bis(2-chloroethoxy)ethane (Cl-DEE) as the solvent.

[0060] The IC of the electrolyte was calculated based on the bulk resistance obtained by electrochemical impedance spectroscopy (EIS) measurements at room temperature. As shown in Table 2, electrolytes comprising Cl-DEE with a boiling point of 235 °C showed high conductivity and high CE, which are crucial for fast charge and long cycle life of Li metal battery.

[0061] As shown in Table 2, the electrolyte of example 1-1 exhibited an IC of 3.8 mS / cm. A lithium metal battery comprising the electrolyte 1-1 exhibited an average CE of 99.21%.Table 2 Electrolyte and its performance according to some embodiments of the present disclosurea: initial CE is initial Li stripping capacity divided by initial Li plating capacity. b: average CE is total Li stripping cycle capacity divided by total Li plating cycle capacity using current density of 1.5 mA / cm2and capacity of 3.0 mAh / cm2[Adv. Energy Mater. 2017, 1702097],EXAMPLE 2

[0062] In this example, electrolytes were prepared and tested similar to Example 1 except that the compositions are shown in Table 3. The solvent was 2-chloroethyl ether (DCE) with a boiling point of 178 °C.Table 3 Electrolytes and their performance according to some embodiments of the present disclosurea: Li / Cu cycle life was determined when the Li / Cu cell fails due to Li consumption or short circuit. [Adv. Energy Mater. 2017, 1702097]

[0063] As shown in Table 3, the electrolytes of examples 2-1, and 2-2 exhibited an IC of 3.78 mS / cm, and 7.31 mS / cm, respectively. Lithium metal batteries comprising the electrolytes exhibited an average Coulombic efficiency (CE) of 99.47%, and 99.42%, respectively. Lithium metal batteries showed a Li / Cu cycle life of 123 and 120 cycles, respectively.

[0064] Fig. 1 shows the cycling performance of Li / Cu coin cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte of Example No. 2- 1 (Ex. No. 2-1). The thickness of Li metal was 50 pm. The current density and capacity used for the Li / Cu cycling were 1.7 mA / cm2and 3.4 mAh / cm2, respectively.EXAMPLE 3

[0065] In this example, electrolytes were prepared and tested similar to Example 2 except that the compositions are shown in Table 4. PYR13FSI was the ionic liquid.

[0066] As shown in Table 4, the electrolytes of examples 3-1, 3-2, 3-3 and 3-4 exhibited an IC of 5.69 mS / cm, 7.83 mS / cm, 6.26 mS / cm, and 4.31 mS / cm, respectively. Lithium metal batteries comprising the electrolytes exhibited an average CE of 99.48%, 99.32%, 99.27% and 99.37%, respectively. Lithium metal batteries showed a Li / Cu cycle life of 117, 123, 125, and 111 cycles, respectively.Table 4 Electrolytes and their performance according to some embodiments of the presentdisclosure

[0067] Fig. 2 shows the cycling performance of Li / Cu coin cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte of Example No. 3- 3 (Ex. No. 3-3). The thickness of Li metal was 50 pm. The current density and capacity used for the Li / Cu cycling were 1.7 mA / cm2and 3.4 mAh / cm2, respectively.EXAMPLE 4

[0068] In this example, electrolytes were prepared and tested similar to Example 3 except that the compositions are shown in Table 5. The solvent was a mixture of 1,2-di ethoxy ethane (DEE, with a boiling point of 121 °C) and DCE.Table 5 Electrolytes and their performance according to some embodiments of the present disclosure

[0069] As shown in Table 5, the electrolytes of examples 4-1 and 4-2 exhibited an IC of 10.29 mS / cm and 10.15 mS / cm, respectively. Lithium metal batteries comprising the electrolytes exhibited an average CE of 99.18% and 99.23%, respectively. Lithium metal batteries showed a Li / Cu cycle life of 137 and 139 cycles, respectively.

[0070] Fig. 3 shows the cycling performance of Li / Cu coin cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte of Example No. 4- 2 (Ex. No. 4-2). The thickness of Li metal was 50 pm. The current density and capacity used for the Li / Cu cycling were 1.7 mA / cm2and 3.4 mAh / cm2, respectively.EXAMPLE 5

[0071] In this example, electrolytes were prepared and tested similar to Example 1 except that the compositions are shown in Table 6-1. The electrochemical performance is summarized in Table 6-2. Comparative example 1 comprises LiFSI and DEE. Comparative example 2 comprises DEE and a fluorinated ether bis(2,2,2-trifluoroethoxy)methane (BTFM) with a boiling point of 107 °C.

[0072] As shown in Table 6-2, the electrolytes of examples 5-1 and 5-2 exhibited an IC of 3.34 mS / cm and 3.84 mS / cm at room temperature (RT), respectively. At a temperature of -20 °C, they exhibit an IC of 0.96 and 1.21 mS / cm, respectively. Lithium metal batteries comprising the electrolytes exhibited an average CE of 99.22%, and 99.24%, respectively.Table 6-1 Electrolyte compositions according to some embodiments of the present disclosureTable 6-2 Electrochemical performance of electrolytesa: Determined when the voltage of Li / Li symmetric cell reaches higher than 0.5 V or lower than -0.5 V during cycling. b: Determined by linear sweep voltammetry from open circuit voltage to 7 V.

[0073] A differential scanning calorimetry (DSC) analysis was also conducted by scanning from 25 to 300 °C at a rate of 5 °C / min in an atmosphere of Argon. The results are summarized in Table 6-3.

[0074] Table 6-3 shows that the comparative example 1 has an enthalpy of 478.42 J / g, which indicates that once the electrolyte starts decomposing, it generates a large amount of heat. Theaddition of a typical fluorinated ether, e.g., bis(2,2,2-trifluoroethoxy)methane (BTFM), lowered the enthalpy from 478.42 J / g to 318.88 J / g. However, the onset decomposing temperature is significantly reduced from 211 °C to 174 °C. It suggests that the fluorinated ether as a solvent deteriorates the thermal stability of the electrolyte. Instead of adding fluorinated ether, the addition of DCE decreased the enthalpy to 166.47 J / g and 251.43 J / g for electrolytes no. 5-1 and 5-2, respectively. They are significantly lower than the comparative examples 1 and 2. Simultaneously, they exhibited a similar onset decomposing temperature in comparison to the comparative example 1. Accordingly, the electrolytes no. 5-1 and 5-2 showed an improved thermal stability and safety.Table 6-3 DSC results of electrolytes 5-1, 5-2 and comparative examples

[0075] Fig. 4 shows the cycling performance of Li / Li symmetric coin cell comprising Li metal as anode, microporous membrane as separator, another Li metal as cathode, and an electrolyte of Example No. 5-1 (Ex. No. 5-1). The thickness of Li metal as anode and cathode were 20 pm and 50 pm, respectively. The current density and capacity used for the Li / Li cycling were 1.5 mA / cm2and 3.0 mAh / cm2, respectively.

[0076] Fig. 5 shows a DSC curve of an electrolyte of comparative example 1. The onset and peak temperature of the exothermic peak were 210.61 °C and 227.50 °C, respectively. The heat generation (enthalpy) of the exothermic peak was 478.42 J / g.

[0077] Fig. 6 shows a DSC curve of an electrolyte of Example No. 5-2 (Ex. No. 5-2). The onset and peak temperature of the exothermic peak were 206.87 °C and 254.16 °C, respectively. The heat generation (enthalpy) of the exothermic peak was 166.47 J / g. The higher peak temperature and lower enthalpy both suggest the electrolyte with DCE shows better thermal stability.EXAMPLE 6

[0078] In this example, electrolyte was prepared and tested similar to Example 3 except that the composition is shown in Table 7. The Li salt was a mixture of LiFSI and LiTFSI.Table 7 Electrolytes and their performance according to some embodiments of the present disclosure

[0079] As shown in Table 7, the electrolyte of examples 6-1 exhibited an IC of 4.26 mS / cm. Lithium metal batteries comprising the electrolyte exhibited an average CE of 99.38%. Lithium metal batteries showed a Li / Cu cycle life of 146 cycles.

[0080] Fig. 7 shows the cycling performance of Li / Cu coin cell comprising Li metal as anode, microporous membrane as separator, Cu foil as cathode, and an electrolyte of Example No. 6- 1 (Ex. No. 6-1). The thickness of Li metal was 50 pm. The current density and capacity used for the Li / Cu cycling were 1.7 mA / cm2and 3.4 mAh / cm2, respectively.EXAMPLE 7

[0081] In this example, electrolyte was prepared and tested similar to Example 3 except that the composition is shown in Table 8. The Li salt was a mixture of LiFSI and LiTFSI.Table 8 Electrolytes and their performance according to some embodiments of the present disclosure

[0082] As shown in Table 8, the electrolyte of examples 7-1 exhibits an IC of 6.46 mS / cm.Lithium metal batteries comprising the electrolyte exhibit an average CE of 99.41%. Lithium metal batteries show a Li / Cu cycle life of 116 cycles.EXAMPLE 8

[0083] In this example, electrolyte was prepared and tested similar to Example 3 except that the composition is shown in Table 9. The ionic liquid was PYR13FSI and EmimFSI.Table 9 Electrolytes and their performance according to some embodiments of the present disclosure

[0084] As shown in Table 9, the electrolyte of examples 8-1 exhibits an IC of 8.09 mS / cm.Lithium metal batteries comprising the electrolyte exhibit an average CE of 99.26%. Lithium metal batteries show a Li / Cu cycle life of 99 cycles.EXAMPLE 9

[0085] In this example, electrolytes were prepared and tested similar to Example 3 except that the compositions are shown in Table 10. The solvent is a mixture of DEE, DCE, and bis(2,2,2- trifluoroethoxy)methane (BTFM).Table 10 Electrolytes and their performance according to some embodiments of the present disclosure

[0086] As shown in Table 10, the electrolytes of examples 9-1 and 9-2 exhibited an IC of 8.52 mS / cm and 6.40 mS / cm, respectively. Lithium metal batteries comprising the electrolytes exhibited an average CE of 99.02% and 99.30%, respectively. Lithium metal batteries show a Li / Cu cycle life of 115 and 195 cycles, respectively.EXAMPLE 10

[0087] An electrolyte comprising a polymer was prepared by mixing Example 2-1 as base electrolyte, pentaerythritol tetraacrylate (PETA) as monomer, and AIBN as initiator followedby polymerization at 65 °C. The composition of the polymer electrolyte prior to curing is shown in Table 11.Table 11 Electrolyte composition of polymer electrolyte prior to curing and electrochemical performance after curing according to some embodiments of the present disclosure

[0088] As shown in Table 11, the electrolyte of examples 10-1 exhibited an IC of 3.82 mS / cm. Lithium metal batteries comprising the electrolyte exhibited an average CE of 99.42%. Lithium metal batteries showed a charge capability of 2C (6.0 mA / cm2), wherein the cell would not be short circuited while charged at the current density and the discharge capacity is 50% or higher at a discharge rate of 1.0 mA / cm2at room temperature.Aspects

[0089] In a first aspect, the present disclosure provides an electrolyte comprising: an electrolyte salt; and an organic solvent, wherein the organic solvent is an ether comprising a non-fluorine halogen substitute and has a boiling point of at least 105 °C.

[0090] In a second aspect according to the first aspect, the organic solvent has a formula of: X- CH2-[CH2OCH2]n-CH2Y 1 < n <15, 1< m < 3, wherein X and Y are each independently selected from the group consisting of H, CEE, C2H5, Cl, Br, I, and CN, and the formula comprises at least one selected from Cl, Br, I, and CN.

[0091] In a third aspect according to the first aspect, the organic solvent has a formula of Z- CH2-[CH2OCH2]n-CH3-mFm, 1 < n <15, 1< m < 3, wherein Z is selected from the group consisting of Cl, Br, I, and CN.

[0092] In a fourth aspect according to any preceding aspect, the organic solvent is an ether with a cyclic structure.

[0093] In a fifth aspect according to any preceding aspect, the organic solvent is not flammable. In some embodiments, the inflammable organic solvent has a flashpoint of 37.8 °C or higher.

[0094] In a sixth aspect according to any preceding aspect, the organic solvent comprises at least one selected from the group consisting of l,2-bis(2-chloroethoxy)ethane, l,2-bis(2- bromoethoxy)ethane, l,2-bis(2-iodoethoxy)ethane, bis[2-(2-chloroethoxy)ethyl] ether, pentaethylene glycol dichloride, bis(2-chloroethyl) ether, bi s(2 -bromoethyl) ether, bis(2- iodoethyl) ether, butyl 2-chloroethyl ether, butyl 2-bromoethyl ether, 3 -ethoxypropionitrile, 1 -chloro-2-(2-fluoroethoxy)ethane, 2-(2-chloroethoxy)- 1 , 1 -difluoroethane, 2-(2- chloroethoxy)- 1,1,1 -trifluoroethane, 1 -bromo-2-(2-fluoroethoxy)ethane, 2-(2-bromoethoxy)- 1 , 1 -difluoroethane, 2-(2 -bromoethoxy)- 1,1,1 -trifluoroethane, 1 -iodo-2-(2- fluoroethoxy)ethane, 2-(2 -iodoethoxy)- 1 , 1 -difluoroethane, 2-(2 -iodoethoxy)- 1,1,1- trifluoroethane, 1 -chloro-2-[2-(2-fluoroethoxy)ethoxy]ethane, 2-[2-(2-chloroethoxy)ethoxy]- 1 , 1 -difluoroethane, 2-[2-(2-chloroethoxy)ethoxy]- 1 ,1,1 -trifluoroethane, 1 -bromo-2-[2-(2- fluoroethoxy)ethoxy] ethane, 2-[2-(2-bromoethoxy)ethoxy]- 1 , 1 -difluoroethane, 2-[2-(2- bromoethoxy)ethoxy]- 1 ,1,1 -trifluoroethane, 1 -iodo-2-[2-(2-fluoroethoxy)ethoxy]ethane, 2- [2- (2-iodoethoxy)ethoxy]- 1 , 1 -difluoroethane, and 2-[2-(2-iodoethoxy)ethoxy]-l , 1,1- trifluoroethane, 2-(chloromethyl)tetrahydrofuran, 2-(bromomethyl)tetrahydrofuran, 2- (iodomethyl)tetrahydrofuran, 3-(chloromethyl)oxolane, 3-(bromomethyl)oxolane, 3- (iodomethyl)oxolane, 2-chlorom ethyl- 1,3 -di oxolane, 4-chlorom ethyl- 1,3 -di oxolane, 2- bromomethyl-l,3-dioxolane, 4-bromomethyl-l,3-dioxolane, and mixtures thereof.

[0095] In a seventh aspect according to any preceding aspect, the organic solvent has a weight percentage in a range from 10 wt% to 95 wt% in the electrolyte.

[0096] In an eighth aspect according to any preceding aspect, the electrolyte further comprises a second organic solvent with a weight percentage in a range from 1 wt% to 40 wt% in the electrolyte.

[0097] In a nineth aspect according to any preceding aspect, the second organic solvent is a fluorinated ether with a boiling point of at least 105 °C.

[0098] In a tenth aspect according to the nineth aspect, the fluorinated ether is selected from the group consisting of bis(2,2,2-trifluoroethoxy)methane (BTFM), l,l,l,3,3,3-hexafluoro-2- (l,l,l,3,3,3-hexafluoropropan-2-yloxymethoxy)propane, bis(3, 3, 3 -trifluoropropoxy )m ethane, l,l,l-trifluoro-3-[(2,2,2-trifluoroethoxy)methoxy]propane, bis(2,2,3,3,3- pentafluoropropoxy)methane, 1,1,1 ,2,2-pentafluoro-3 -((2,2,2- trifluoroethoxy)methoxy)propane, 1 , 1 ,2,2-tetrafluoroethyl-2,2, 3 ,3 -tetrafluoropropyl ether (TTE), lH,lH,5H-octafluoropentyl-l,l,2,2-tetrafluoroethyl ether (OTE), bis(2,2,2- trifluoroethyl) ether, 1H,1H,2’H-Perfluorodipropyl ether, 2,2,2-Trifluoroethyl 1, 1,2,2- tetrafluoroethyl ether, 1,2-(1,1,2,2-Tetrafluoroethoxy)ethane (TFEE), tris(2,2,2- trifluoroethyl)orthoformate (TFEO) and mixtures thereof.

[0099] In an eleventh aspect according to any preceding aspect, the electrolyte further comprises an ionic liquid with a weight percentage in a range from 1 wt% to 80 wt% in the electrolyte.

[0100] In a twelfth aspect according to the eleventh aspect, the ionic liquid has one formula ofor , wherein Ri, R2, R3 are independently selected from the group consisting of hydrogen, Ci-is alkyl, Ci-is haloalkyl, Ci-is hydroxyalkyl, Ci-18 aminoalkyl, C2-18 alkenyl, C2-18 alkynyl, and Ce-18 aryl, n is an integer having a value in a range from 1 to 6, R4 and Rs are independently selected from the group consisting of Ci-is alkyl, Ci-is haloalkyl, Ci-is hydroxyalkyl, Ci-is aminoalkyl, C2-18 alkenyl, C2-18 alkynyl, and Ce-18 aryl, and X' is an anion. In some embodiments, wherein the anion X' is selected from the group consisting of bis(fluorosulfonyl)imide (FSI‘), bis(trifluoromethanesulfonyl)imide (TFSF),hexafluorophosphate (PFe’), tetrafluoroborate (BFF), bis(oxalate)borate (BOB’), difluoro(oxalato)borate (DFOB’), trifluoromethanesulfonate (TfO’), nitrate (NO3 ), dicyanamide (DC A'), fluoride (F‘), chloride (Cl’), bromide (Br ), and mixtures thereof.

[0101] In a thirteenth aspect according to the eleventh or twelfth aspect, the ionic liquid is selected from the group consisting of l-ethyl-3-methylimidazolium bis(fluorosulfonyl) imide(EmimFSI), l-butyl-3 -methylimidazolium bis(fluorosulfonyl) imide (BmimFSI), l-hexyl-3- methylimidazolium bis(fluorosulfonyl) imide (HmimFSI), 1 -vinyl-3 -methylimidazolium bis(fluorosulfonyl) imide (VmimFSI), l-ethyl-3 -methylimidazolium bis(trifluorom ethanesulfonyl) imide (EmimTFSI), l-butyl-3 -methylimidazolium bi s(trifluorom ethanesulfonyl) imide (BmimTFSI), l-hexyl-3 -methylimidazolium bis(trifluoromethanesulfonyl) imide (HmimTFSI), 1 -vinyl-3 -methylimidazolium bi s(trifluorom ethanesulfonyl) imide (VmimTFSI), N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), N -propyl -N -methy Ipy rroli dinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI) 1 -butyl- 1 -methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI), 1 -butyl- 1 -methylpyrrolidinium bis(oxalate)borate(PYR14B0B), 1 -butyl- 1 -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide(PYR14TFSI), 1 -butyl- 1 -methylpyrrolidinium di cyanamide (PYR14DCA), 1 -butyl- 1- methylpyrrolidinium trifluoromethanesulfonate (PYR14TfO), 1 -methyl- 1 -(2- methoxyethyl)pyrrolidinium bis(fluorosulfonyl)imide (PYOFSI), 1 -methyl- 1- pentylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR15TFSI), 1 -methyl- 1- octylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR18TFSI), N-propyl-N- methylpiperidinium bis(fluorosulfonyl)imide, N-propyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1 -methylpiperidinium bis(fluorosulfonyl)imide,1 -butyl- 1 -methylpiperidinium bi s(oxal ate)b orate, 1 -butyl- 1 -methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1 -methylpiperidinium di cyanamide, 1 -butyl- 1- methylpiperidinium trifluoromethanesulfonate, 1 -methyl- 1 -(2 -m ethoxy ethyl)piperidiniumbis(fluorosulfonyl)imide, 1 -methyl- 1-pentylpiperidinium bis(trifluoromethanesulfonyl)imide,1 -methyl- 1-octylpiperidinium bis(trifluoromethanesulfonyl)imide, N-propyl-N- methylazepanium bis(fluorosulfonyl)imide, N-propyl-N-methylazepanium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1-methylazepanium bis(fluorosulfonyl)imide, 1- butyl- 1 -methylazepanium bis(oxalate)borate, 1 -butyl- 1 -methylazepanium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1 -methyl azepanium dicyanamide, 1-butyl-l- methylazepanium trifluoromethanesulfonate, 1 -methyl- 1 -(2-methoxyethyl)azepanium bis(fluorosulfonyl)imide, 1 -methyl- 1-pentylazepanium bis(trifluoromethanesulfonyl)imide, 1- methyl-l-octylazepanium bis(trifluoromethanesulfonyl)imide and mixtures thereof.

[0102] In a fourteenth aspect according to any preceding aspect, the electrolyte salt is selected from the group consisting of lithium bis(fluorosulfonyl) imide (LiFSI), lithium perchlorate (LiCICh), lithium hexafluorophosphate (LiPFe), lithium borofluoride (LiBF4), lithium hexafluoroarsenide (LiAsFe), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium nitrate (LiNCh), lithium fluoroalkylphosphates (Li[PFx(CyF2y+i-zHz)6-x]) (l<x<5, l<y<8, and 0<z<2y-l), lithium bis(perfluoroethanesulfonyl)imide (LiBETI), lithium difluoro(oxalato)borate (LiDFOB), lithium fluorophosphate (Li2PO3F), lithium difluoro(bisoxalato)phosphate (LiC4PO8F2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium difluorophosphate (LiDFP), LiC(CF3SO2)3, LiF, LiCl, LiBr, Lil, Li2SO4, LisPCh, Li2CO3, lithium acetate, lithium trifluoromethyl acetate, lithium oxalate, and mixtures thereof

[0103] In a fifteenth aspect according to any preceding aspect, the electrolyte salt has a weight percentage in a range from 10 wt% to 50 wt% in the electrolyte.

[0104] In a sixteenth aspect according to any preceding aspect, the electrolyte is chemically stable in the presence of lithium metal.

[0105] In a seventh aspect according to any preceding aspect, the electrolyte further comprises a polymer with a weight percentage in a range from 0.02 wt% to 40 wt% in the electrolyte. In some embodiments, the polymer is in situ polymerized after mixing a monomer with the electrolyte salt and the organic solvent.

[0106] In an eighteenth aspect according to the seventeenth aspect, the monomer is selected from the group consisting of 2,2,3,3-tetrafluorobutane-l,4-diacrylate, 2, 2, 3, 3, 4, 4,5,5- octafluorohexane-l,6-diyl diacrylate, 2,2,3,3,4,4,5,5-octafluorohexane-l,6-diyl bis(2- methylacrylate), poly(ethylene glycol) diacrylate (Mn=700), triethylene glycol dimethacrylate (TEGDMA), diurethane dimethacrylate, tetraallyl silane (TAS), 2,4,6,8-tetramethyl-2,4,6,8- tetravinylcyclotetrasiloxane, triethoxyvinylsilane, allyltriethoxysilane, pentaerythritol tetraacrylate (PETA), pentaerythritol tetramethacrylate (PETMA), tris[2-(acryloyloxy)ethyl] isocyanurate (TAEI), di(trimethylolpropane) tetraacrylate (Di-TMPTA), trimethylolpropane propoxylate triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0107] In a nineteenth aspect according to any preceding aspect, the electrolyte does not include any solvent that has a boiling point less than 105 °C.

[0108] In a twentieth aspect according to any preceding aspect, each component in the electrolyte has a boiling point of 120 °C or higher.

[0109] In a twenty-first aspect according to any preceding aspect, the electrolyte does not exhibit any exothermic or endothermic peak in a differential scanning calorimetry (DSC) curve from room temperature to 110 °C. In some embodiments, the electrolyte does not exhibit any exothermic or endothermic peak in a DSC curve from room temperature to 105 °C.

[0110] In a twenty-second aspect according to any preceding aspect, the electrolyte exhibits an ionic conductivity (IC) of at least 1.0 mS / cm at room temperature.[OHl] In a twenty-third aspect, the present disclosure provides an electrochemical device comprising an electrolyte according to any preceding aspect and an anode.

[0112] In a twenty-fourth aspect according to the twenty -third aspect, the anode comprises lithium metal or lithium alloy.

[0113] In a twenty-fifth aspect according to the twenty-third or twenty-fourth aspect, the electrochemical device is free of venting during charge or discharge.

[0114] In a twenty-sixth aspect according to any of the twenty-third through twenty-fifth aspects, the electrochemical device exhibits an average Coulombic efficiency (CE) of at least 98.0%.

[0115] In a twenty-seventh aspect according to any of the twenty-third through twenty-sixth aspects, the electrochemical device passes a safety test such as a hotbox test, wherein the electrochemical device is at 100% state-of-charge and is held at each of the following temperatures: 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, and 190 °C for 10 minutes with a European Council for Automotive Research (EUCAR) hazard level of 4 or below.

[0116] In a twenty-eighth aspect according to any of the twenty-third through twenty-seventh aspects, the electrochemical device does not experience leakage of the electrolyte after the hotbox test.

[0117] In a twenty-nineth aspect according to any of the twenty-third through twenty-eighth aspects, the electrochemical device does not explode after the hotbox test.

[0118] In a thirtieth aspect according to any of the twenty -third through twenty-nineth aspects, the electrochemical device experiences a weight loss of 50% or less of the total weight of electrolyte in the device after the hotbox test.

[0119] Various embodiments of the features of this disclosure are described herein. However, it should be understood that such embodiments are provided merely by way of example, and numerous variations, changes, and substitutions can occur to those skilled in the art without departing from the scope of this disclosure. It should also be understood that various alternatives to the specific embodiments described herein are also within the scope of this disclosure.

Claims

We claim:

1. An electrolyte comprising: a) an electrolyte salt; and b) an organic solvent with a weight percentage in a range from 10 wt% to 95 wt% in the electrolyte, wherein the organic solvent is an ether comprising a non-fluorine halogen substitute and has a boiling point of at least 105 °C.

2. The electrolyte of claim 1, wherein the organic solvent has a formula of:X-CH2-[CH2OCH2]n-CH2Y 1 < n <15, 1< m < 3, wherein X and Y are each independently selected from the group consisting of H, CH3, C2H5, Cl, Br, I, and CN, and the formula comprises at least one selected from Cl, Br, I, and CN.

3. The electrolyte of claim 1, wherein the organic solvent has a formula of Z-CH2- [CH2OCH2]n-CH3-mFm, 1 < n <15, 1< m < 3, wherein Z is selected from the group consisting of Cl, Br, I, and CN.

4. The electrolyte of claim 1, wherein the organic solvent comprises at least one selected from the group consisting of l,2-bis(2-chloroethoxy)ethane, l,2-bis(2-bromoethoxy)ethane, 1,2- bis(2-iodoethoxy)ethane, bis[2-(2-chloroethoxy)ethyl] ether, pentaethylene glycol dichloride, bis(2-chloroethyl) ether, bi s(2 -bromoethyl) ether, bis(2-iodoethyl) ether, butyl 2-chloroethyl ether, butyl 2-bromoethyl ether, 3 -ethoxypropionitrile, l-chloro-2-(2- fluoroethoxy)ethane, 2-(2-chloroethoxy)- 1 , 1 -difluoroethane, 2-(2-chloroethoxy)- 1,1,1- trifluoroethane, l-bromo-2-(2-fluoroethoxy)ethane, 2-(2 -bromoethoxy)- 1, 1 -difluoroethane, 2-(2 -bromoethoxy)- 1,1,1 -trifluoroethane, 1 -iodo-2-(2-fluoroethoxy)ethane, 2-(2- iodoethoxy)- 1 , 1 -difluoroethane, 2-(2 -iodoethoxy)- 1,1,1 -trifluoroethane, 1 -chloro-2-[2-(2- fluoroethoxy)ethoxy] ethane, 2-[2-(2-chloroethoxy)ethoxy]- 1 , 1 -difluoroethane, 2-[2-(2-chloroethoxy)ethoxy]- 1,1,1 -trifluoroethane, 1 -bromo-2-[2-(2-fluoroethoxy)ethoxy] ethane,2-[2-(2-bromoethoxy)ethoxy]- 1 , 1 -difluoroethane, 2-[2-(2-bromoethoxy)ethoxy]-l , 1,1- trifluoroethane, 1 -iodo-2-[2-(2-fluoroethoxy)ethoxy]ethane, 2-[2-(2-iodoethoxy)ethoxy]- 1,1 -difluoroethane, and 2-[2-(2-iodoethoxy)ethoxy]- 1,1,1 -trifluoroethane, 2- (chloromethyl)tetrahydrofuran, 2-(bromomethyl)tetrahydrofuran, 2-(iodomethyl)tetrahydrofuran, 3-(chloromethyl)oxolane, 3-(bromomethyl)oxolane, 3- (iodomethyl)oxolane, 2-chlorom ethyl- 1,3 -di oxolane, 4-chlorom ethyl- 1,3 -di oxolane, 2- bromomethyl-l,3-dioxolane, 4-bromomethyl-l,3-dioxolane, and mixtures thereof.

5. The electrolyte of claim 1, further comprising a second organic solvent with a weight percentage in a range from 1 wt% to 40 wt% in the electrolyte, and wherein the second organic solvent is a fluorinated ether with a boiling point of at least 105 °C.

6. The electrolyte of claim 5, wherein the fluorinated ether is selected from the group consisting of bis(2,2,2-trifluoroethoxy)methane (BTFM), l,l,l,3,3,3-hexafluoro-2- ( 1 , 1 , 1 ,3 , 3 ,3 -hexafluoropropan-2-yl oxymethoxy)propane, bi s(3 , 3 ,3 - trifluoropropoxy)methane, l,l,l-trifluoro-3-[(2,2,2-trifluoroethoxy)methoxy]propane, bis(2,2,3,3,3-pentafluoropropoxy)methane, 1, 1,1,2, 2-pentafluoro-3 -((2,2,2- trifluoroethoxy)methoxy)propane, l,l,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), lH,lH,5H-octafluoropentyl-l,l,2,2-tetrafluoroethyl ether (OTE), bis(2,2,2- trifluoroethyl) ether, 1H,1H,2’H-Perfluorodipropyl ether, 2,2,2-Trifluoroethyl 1, 1,2,2- tetrafluoroethyl ether, 1,2-(1,1,2,2-Tetrafluoroethoxy)ethane (TFEE), tris(2,2,2- trifluoroethyl)orthoformate (TFEO) and mixtures thereof.

7. The electrolyte of claim 1, further comprising an ionic liquid with a weight percentage in a range from 1 wt% to 80 wt% in the electrolyte, wherein the ionic liquid has one formula ofwherein Ri, R2, R3 are independently selected from the group consisting of hydrogen, Ci-is alkyl, Ci-is haloalkyl, Ci-18 hydroxyalkyl, Ci-18 aminoalkyl, C2-18 alkenyl, C2-18 alkynyl, and Ce-18 aryl, n is an integer having a value in a range from 1 to 6, R4 and Rs are independently selected from the group consisting of Ci-is alkyl, Ci-is haloalkyl, Ci-is hydroxyalkyl, Ci-is aminoalkyl, C2-18 alkenyl, C2-18 alkynyl, and Ce-18 aryl, and X' is an anion.

8. The electrolyte of claim 7, wherein the ionic liquid is selected from the group consisting of l-ethyl-3 -methylimidazolium bis(fluorosulfonyl) imide (EmimFSI), l-butyl-3- methylimidazolium bis(fluorosulfonyl) imide (BmimFSI), l-hexyl-3-methylimidazolium bis(fluorosulfonyl) imide (HmimFSI), 1 -vinyl-3 -methylimidazolium bis(fluorosulfonyl) imide (VmimFSI), l-ethyl-3 -methylimidazolium bi s(trifluorom ethanesulfonyl) imide(EmimTFSI), l-butyl-3 -methylimidazolium bi s(tri fluoromethanesulfonyl) imide(BmimTFSI), l-hexyl-3 -methylimidazolium bi s(tri fluoromethanesulfonyl) imide(HmimTFSI), 1 -vinyl-3 -methylimidazolium bi s(tri fluoromethanesulfonyl) imide(VmimTFSI), N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), N- propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI) 1-butyl-1 -methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI), 1 -butyl- 1- methylpyrrolidinium bis(oxalate)borate (PYR14B0B), 1 -butyl- 1 -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI), 1 -butyl- 1 -methylpyrrolidinium dicyanamide (PYR14DCA), 1 -butyl- 1 -methylpyrrolidinium trifluoromethanesulfonate(PYR14TfO), 1 -methyl- 1 -(2 -m ethoxy ethyl)pyrrolidinium bis(fluorosulfonyl)imide(PYOFSI), 1 -methyl- 1-pentylpyrrolidinium bis(trifluoromethanesulfonyl)imide(PYR15TFSI), 1 -methyl- 1-octylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR18TFSI), N-propyl-N-methylpiperidinium bis(fluorosulfonyl)imide, N-propyl-N- methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1-methylpiperidinium bis(fluorosulfonyl)imide, 1 -butyl- 1-methylpiperidinium bis(oxalate)borate, 1-butyl-l- methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -butyl- l-methylpiperidinium di cyanamide, 1 -butyl- 1-methylpiperidinium trifluorom ethanesulfonate, 1 -methyl- 1 -(2- methoxyethyl)piperidinium bis(fluorosulfonyl)imide, 1 -methyl- 1-pentylpiperidinium bis(trifluoromethanesulfonyl)imide, 1 -methyl- 1 -octylpiperidinium bis(trifluoromethanesulfonyl)imide, N-propyl-N-methylazepanium bis(fluorosulfonyl)imide, N-propyl-N-methylazepanium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1-methylazepanium bis(fluorosulfonyl)imide, 1 -butyl- 1 -methylazepanium bis(oxalate)borate, 1 -butyl- 1 -methylazepanium bis(trifluoromethanesulfonyl)imide, 1 -butyl- 1 -methyl azepanium di cyanamide, 1 -butyl- 1- methylazepanium trifluorom ethanesulfonate, 1 -methyl- 1 -(2-methoxyethyl)azepanium bis(fluorosulfonyl)imide, 1 -methyl- 1 -pentylazepanium bis(trifluoromethanesulfonyl)imide, 1 -methyl- 1 -octylazepanium bis(trifluoromethanesulfonyl)imide and mixtures thereof.

9. The electrolyte of claim 1, wherein the electrolyte salt is selected from the group consisting of lithium bis(fluorosulfonyl) imide (LiFSI), lithium perchlorate (LiCKN), lithium hexafluorophosphate (LiPFe), lithium borofluoride (LiBF4), lithium hexafluoroarsenide (LiAsFe), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium nitrate (LiNCh), lithium fluoroalkylphosphates (Li[PFx(CyF2y+i-zHz)6-x]) (l<x<5, l<y<8, and 0<z<2y-l), lithium bis(perfluoroethanesulfonyl)imide (LiBETI), lithium difluoro(oxalato)borate (LiDFOB), lithium fluorophosphate (Li2PO3F), lithiumdifluoro(bisoxalato)phosphate (LiC4PO8F2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium difluorophosphate (LiDFP), LiC(CF3SO2)3, LiF, LiCl, LiBr, Lil, Li2SO4, LisPCh, Li2CO3, lithium acetate, lithium trifluoromethyl acetate, lithium oxalate, and mixtures thereof10. The electrolyte of claim 1, wherein the electrolyte salt has a weight percentage in a range from 10 wt% to 60 wt%.

11. The electrolyte of claim 1, further comprising a polymer with a weight percentage in a range from 0.02 wt% to 40 wt% in the electrolyte, wherein the polymer is in situ polymerized after mixing a monomer with the electrolyte salt and the organic solvent.

12. The electrolyte of claim 11, wherein the monomer is selected from the group consisting of 2,2,3,3-tetrafluorobutane-l,4-diacrylate, 2,2,3,3,4,4,5,5-octafluorohexane-l,6-diyl diacrylate, 2,2,3,3,4,4,5,5-octafluorohexane-l,6-diyl bis(2-methylacrylate), poly(ethylene glycol) diacrylate (Mn= 500 - 5000), triethylene glycol dimethacrylate (TEGDMA), diurethane dimethacrylate, tetraallyl silane (TAS), 2,4,6,8-tetramethyl-2,4,6,8- tetravinylcyclotetrasiloxane, triethoxyvinylsilane, allyltriethoxysilane, pentaerythritol tetraacrylate (PETA), pentaerythritol tetramethacrylate (PETMA), tris[2- (acryloyloxy)ethyl] isocyanurate (TAEI), di(trimethylolpropane) tetraacrylate (Di- TMPTA), trimethylolpropane propoxylate triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

13. The electrolyte of claim 1, wherein the electrolyte does not include any solvent that has a boiling point less than 105 °C.

14. An electrochemical device comprising the electrolyte of claim 1 and an anode.

15. The electrochemical device of claim 14, wherein the anode comprises lithium metal or lithium alloy.

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