Electrolyte comprising four or more salts and lithium metal batteries comprising same

Abstract

Provided herein are electrolyte compositions comprising four or more salts dissolved in a solvent, wherein the four or more salts are chemically stable with each other in the presence of the solvent, and the electrolyte is stable in presence of lithium metal. In some embodiments, the electrolyte is substantially free of PF6 -, such as LiPF6. In some embodiments, the electrolyte comprises LiFSI. In some embodiments, the electrolyte comprises a nitrate salt. In some embodiments, an electrochemical device comprising the electrolyte exhibits an improved cycling performance. In some embodiments, the electrochemical device is a lithium metal battery.

Description

ELECTROLYTE COMPRISING FOUR OR MORE SALTS AND LITHIUM METAL BATTERIES COMPRISING SAMECROSS-REFERENCE

[0001] The present application claims the benefit of US Serial No. 63 / 672,896, filed July 18, 2024, and US Serial No. 63 / 662,510, filed June 21, 2024, the entire content of which is incorporated herein by reference into this application.TECHNICAL FIELD

[0002] This disclosure relates to various electrolyte compositions comprising four or more salts suitable for lithium metal batteries.BACKGROUND

[0003] Lithium metal batteries are widely investigated for the relatively higher energy density due to use of lithium metal as anode. Because of the high reactivity of lithium metal, electrolyte becomes a critical aspect for developing lithium metal battery with a desirable stability and cycle life. Electrolytes usually exist in a liquid or semi-solid state and comprise a non-aqueous solvent. Even there are numbers of lithium salts that can be potentially used in electrolyte, solubility of lithium salt in the solvent is important. Furthermore, an electrolyte usually comprises multiple salts, their solubilities and stabilities in the presence of another salt are also critical for electrolyte design. For example, stability of lithium hexafluorophosphate (LiPFe) is relatively poor in the presence of ether solvent. Nitrate salt such as lithium nitrate (LiNCh) exhibits a poor solubility in ether solvent. Carbonate solvents may lead to low Coulombic efficiency (CE) and short cycle life. Thus, there remains a need for new electrolytes.SUMMARY

[0004] The present disclosure provides an electrolyte of a lithium metal battery, the electrolyte comprising four or more salts dissolved in a solvent, wherein the four or more salts are chemically stable with each other and with the solvent, and the electrolyte is stable in presence of lithium metal.

[0005] In some embodiments, the electrolyte is substantially free of PFe', such as LiPFe.

[0006] In some embodiments, the electrolyte comprises LiFSI.

[0007] In some embodiments, the electrolyte comprises a nitrate salt. In some embodiments, the nitrate salt is an alkali metal nitrate salt. In some embodiments, the nitrate salt is lithium nitrate (LiNCh).

[0008] In some embodiments, an electrochemical device comprising the electrolyte exhibits an improved cycling performance.

[0009] In some embodiments, the solvent comprises an ether. In some embodiments, the solvent comprises a non-halogenated ether. In some embodiments, the solvent comprises a non-halogenated ether and a fluorinated ether. In some embodiments, the fluorinated ether has a boiling point of at least 100 °C at 1 atm.[00101 In some embodiments, the electrolyte further comprises a polymer with a weight percentage in a range from 0.1 wt% to 50 wt% in the electrolyte. In some embodiments, the electrolyte is a semisolid electrolyte or gel electrolyte.

[0011] The term “% by weight” or “percent by weight” refers to the percentage the identified components or components represent with the percent calculated as percent by weight of all components.

[0012] “Alkyl” refers to a radical of a straight-chain or branched saturated hydrocarbon group having from 1 to 20 carbon atoms (“C1-20 alkyl”). In some embodiments, an alkyl group has 1 to 10 carbon atoms (“Ci -10 alkyl”). In some embodiments, an alkyl group has 1 carbon atom (“Ci alkyl”). Examples of C1-6 alkyl groups include methyl (Ci), ethyl (C2), n-propyl (C3), isopropyl (C3), n-butyl (C4), tertbutyl (C4), sec-butyl (C4), isobutyl (C4), n-pentyl (C5), 3-pentanyl (Cs), amyl (Cs), neopentyl (C5), 3- methyl-2-butanyl (Cs), tertiary amyl (Cs), and n-hexyl (Ce). Additional examples of alkyl groups include n-heptyl (C7), n-octyl (Cs) and the like. Unless otherwise specified, each instance of an alkyl group is independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents, e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. In certain embodiments, the alkyl group is unsubstituted C1-10 alkyl (e.g., -CH3). In certain embodiments, the alkyl group is substituted C1-10 alkyl. Common alkyl abbreviations include Me (-CH3), Et (-CH2CH3), i-Pr (-CH(CH3)2), n-Pr (- CH2CH2CH3), n-Bu (-CH2CH2CH2CH3), or i-Bu (-CH2CH(CH3)2).

[0013] The term “halogen” refers to fluoro (F), chloro (Cl), bromo (Br), or iodo (I).

[0014] The term “oxo” refers to a divalent doubly bonded oxygen atom (i.e., “=O”). As used herein, oxo groups are attached to carbon atoms to form carbonyls.

[0015] The term “alkoxy” refers to an -O-alkyl radical (e.g., -OCH3).

[0016] The term “haloalkyl” refers to an alkyl, in which one or more hydrogen atoms is / are replaced with an independently selected halogen.

[0017] The term “fluoroalkyl” refers to an alkyl, in which one or more hydrogen atoms is / are replaced with a fluorine.

[0018] The term “aryl” refers to a 6-20 membered all carbon ring system wherein at least one ring in the system is aromatic (e.g., 6-carbon monocyclic, 10-carbon bicyclic, or 14-carbon tricyclic aromatic ring system). Examples of aryl groups include phenyl, naphthyl, tetrahydronaphthyl, and the like.

[0019] “Cycloalkyl” refers to a radical of a non-aromatic cyclic hydrocarbon group having from 3 to 10 ring carbon atoms (“C3-C10 cycloalkyl”) and zero heteroatoms in the nonaromatic ring system. In some embodiments, “C3-C10 cycloalkyl” is a saturated monocyclic group having from 3 to 10 ring carbon atoms. Examples of C3-C10 cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Unless otherwise specified, each instance of a cycloalkyl group is independently unsubstituted (an “unsubstituted cycloalkyl”) or substituted (a “substituted cycloalkyl”) with one or more substituents. In certain embodiments, the cycloalkyl group is unsubstituted C3-C10 cycloalkyl. In certain embodiments, the cycloalkyl group is substituted C3-C10 cycloalkyl.

[0020] “Halocycloalkyl” refers to a radical of a non-aromatic cyclic hydrocarbon group having from 3 to 10 ring carbon atoms (“C3-10 cycloalkyl”) and at least one halogen either in the substituent or in the nonaromatic ring.

[0021] The term “heteroaryl”, as used herein, refers to a ring system having 5 to 20 ring atoms, such as 5, 6, 9, 10, or 14 ring atoms; wherein at least one ring in the system contains one or more heteroatoms independently selected from the group consisting of N, O, S, Si, and B, and at least one ring in the system is aromatic (but does not have to be a ring which contains a heteroatom, e.g. tetrahydroisoquinolinyl, e.g., tetrahydroquinolinyl). Heteroaryl groups can include monocyclic, bridged, fused, and spiro ring systems, so long as one ring in the system is aromatic. Examples of heteroaryl include thienyl, pyridinyl, furyl, oxazolyl, oxadiazolyl, pyrrolyl, imidazolyl, triazolyl, thiodiazolyl, pyrazolyl, isoxazolyl, thiadiazolyl, pyranyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, thiazolyl benzothienyl, benzoxadiazolyl, benzofuranyl, benzimidazolyl, benzotriazolyl, cinnolinyl, indazolyl, indolyl, isoquinolinyl, isothiazolyl, naphthyridinyl, purinyl, thienopyridinyl, pyrido[2,3- ]pyrimidinyl, pyrrolo[2,3-Z>]pyridinyl, quinazolinyl, quinolinyl, thieno[2,3-c]pyridinyl, pyrazolo[3,4-£>]pyridinyl, pyrazolo[3,4-c]pyridinyl, pyrazolo[4,3-c]pyridine, pyrazolo[4,3- Z>]pyridinyl, tetrazolyl, chromane, 2,3-dihydrobenzo[ / >][l,4]dioxine, benzo[ ][ 1,3] di oxole, 2,3- dihydrobenzofuran, tetrahydroquinoline, 2,3-dihydrobenzo[ / >][l,4]oxathiine, isoindoline, and others. In some embodiments, the heteroaryl is selected from thienyl, pyridinyl, furyl, pyrazolyl, imidazolyl, isoindolinyl, pyranyl, pyrazinyl, and pyrimidinyl. For purposes of clarification, heteroaryl also includes aromatic lactams, aromatic cyclic ureas, or vinylogous analogs thereof, in which each ringnitrogen adjacent to a carbonyl is tertiary (i.e., all three valences are occupied by non-hydrogen substituents), such as one or more of pyridine, wherein each ring nitrogen adjacent to a carbonyl is tertiary (i.e., the oxo group (i.e., “=O”) herein is a constituent part of the heteroaryl ring).

[0022] The term “heterocyclyl” refers to a saturated or partially unsaturated ring systems with 3-16 ring atoms (e.g., 3-8 membered monocyclic, 5-12 membered bicyclic, or 10-14 membered tricyclic ring system) having at least one heteroatom selected from O, N, S, Si, and B, wherein one or more ring atoms may be substituted by 1-3 oxo (forming, e.g., a lactam) and one or more N or S atoms may be substituted by 1-2 oxido (forming, e.g., an N-oxide, an S-oxide, or an S,S-dioxide), valence permitting. Heterocyclyl groups include monocyclic, bridged, fused, and spiro ring systems.Examples of heterocyclyl groups include piperazinyl, pyrrolidinyl, dioxanyl, morpholinyl, tetrahydrofuranyl, tetrahydropyridyl, dihydropyrazinyl, dihydropyridyl, dihydropyrrolyl, dihydrofuranyl, dihydrothiophenyl, and the like. Heterocyclyl may include multiple fused and bridged rings. Non-limiting examples of fused / bridged heteorocyclyl includes: 2-azabicyclo[1.1.0]butane, 2- azabicyclo[2. 1 .0]pentane, 2-azabicyclo[l . 1 . 1 ]pentane, 3-azabicyclo[3. 1 .0]hexane, azabicy clo[2. 1 . 1 ]hexane, 3-azabicyclo[3.2.0]heptane, octahydrocyclopenta[c]pyrrole, azabicyclo[4. 1 .0]heptane, 7-azabicyclo[2.2.1]heptane, 6-azabicyclo[3.1.1 ]heptane. 7- azabicyclo[4.2.0]octane, 2-azabicyclo[2.2.2]octane, 3-azabicyclo[3.2.1 ]octane, 2- oxabicyclo[ 1. 1.0]butane, 2-oxabicyclo[2. 1.0]pentane, 2-oxabicyclo[ 1.1.1 ]pentane, 3- oxabicyclo[3. 1 .0]hexane, 5-oxabicyclo[2. 1 . l]hexane, 3-oxabicyclo[3.2.0]heptane, 3- oxabicyclo[4.1.0]heptane, 7-oxabicyclo[2.2.1]heptane, 6-oxabicyclo[3.1.1]heptane, 7- oxabi cy cl o [4.2.0] octane, 2-oxabicyclo[2.2.2]octane, 3-oxabicyclo[3.2.1]octane, and the like.Heterocyclyl also includes spirocyclic rings (e.g., spirocyclic bicycle wherein two rings are connected through just one atom). Non-limiting examples of spirocyclic heterocyclyls include 2- azaspiro[2.2]pentane, 4-azaspiro[2.5]octane, l -azaspiro[3.5]nonane, 2-azaspiro[3.5]nonane, 7- azaspiro[3.5]nonane, 2-azaspiro[4.4]nonane, 6-azaspiro[2.6]nonane, l,7-diazaspiro[4.5]decane, 7- azaspiro[4.5]decane 2,5-diazaspiro[3.6]decane, 3-azaspiro[5.5]undecane, 2-oxaspiro[2.2]pentane, 4- oxaspiro[2.5]octane, l-oxaspiro[3.5]nonane, 2-oxaspiro[3.5]nonane, 7-oxaspiro[3.5]nonane, 2- oxaspiro[4.4]nonane, 6-oxaspiro[2.6]nonane, l,7-dioxaspiro[4.5]decane, 2,5-dioxaspiro[3.6]decane, l-oxaspiro[5.5]undecane, 3-oxaspiro[5.5]undecane, 3-oxa-9-azaspiro[5.5]undecane and the like.

[0023] The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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 shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure.

[0025] FIG. 1 shows the cycling performance of a pouch cell comprising example 2-1 as electrolyte in view of specific discharge capacity according to one embodiment of the present disclosure.

[0026] FIG. 2 shows the cycling performance of a pouch cell comprising example 2-1 as electrolyte in view of discharge capacity retention according to one embodiment of the present disclosure.

[0027] FIG. 3 shows the cycling performance of a pouch cell comprising example 2-1 as electrolyte in view of coulombic efficiency (CE) according to one embodiment of the present disclosure.DETAILED DESCRIPTION

[0028] The present disclosure generally relates to electrolyte compositions suitable for various electrochemical devices. In some embodiments, the electrolyte comprises multiple salts. In some embodiments, the electrolyte comprises four or more salts.

[0029] In some embodiments, the electrolyte is substantially free of hexafluorophosphate (PFe).

[0030] In some embodiments, the electrolyte comprises lithium bis(fluorosulfonyl)imide (LiFSI).

[0031] In some embodiments, the electrolyte comprises a nitrate (alternatively nitrate salt) such as lithium nitrate (LiNCh). In some embodiments, the nitrate is at least one selected from the group consisting of silver nitrate (AgNOs), sodium nitrate, potassium nitrate, zinc nitrate, magnesium nitrate, aluminum nitrate, and calcium nitrate.

[0032] In some embodiments, the nitrate is an ionic liquid. In some embodiments, the ionic liquid with nitrate as anion includes tetraalkylammonium nitrate, tetraalkylphosphonium nitrate, 1 -alkyl-3- alkylimidazolium nitrate, and cyclic quaternary ammonium nitrate such as N-alkyl-N- alkylpyrrolidinium nitrate, N-alkyl-N-alkylpiperidinium nitrate, and N-alkyl-N-alkylazepanium nitrate. Non-limiting specific ionic liquid nitrate salts include tetraethylammonium nitrate, tetrabutylammonium nitrate, tributylmethylphosphonium nitrate, l-ethyl-3-methylimidazolium nitrate, N-propyl-N-methylpyrrolidinium nitrate, N-propyl-N-methylpiperidinium nitrate, and N- propyl-N-methylazepanium nitrate.

[0033] In some embodiments, the electrolyte comprises LiFSI, a nitrate salt and at least two salts selected from the group consisting of lithium perchlorate (LiCIC ), lithium tetrafluoroborate (LiBF-t), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bis(perfluoroethylsulfonyl)imide (LiBETI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFsSO2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiBF2C2O4, LiDFOB), lithium fluorophosphate (Li2PChF), lithium difluorophosphate (LiDFP), lithium difluoro(bisoxalato)phosphate (LiC4POsF2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)s), lithium 4,5-dicyano-2-trifluoromethylimidazole (LiTDI), lithium acetate, lithium trifluoromethyl acetate.

[0034] In some embodiments, the salts are dissolved in a solvent. In some embodiments, the solvent comprises an organic ether. In some embodiments, the solvent comprises a non-halogenated ether. In some embodiments, the solvent comprises a first non-halogenated ether and a second halogenated (fluorinated) ether.

[0035] Nitrate salt exhibits poor solubility in an organic solvent such as 1,2-diethoxy ethane (DEE), especially in the presence of another salt at a high concentration. To ensure desired solubility of nitrate salt, higher polar solvents such as 1,2-dimethoxyethane (DME) may be used. However, DME may exhibit poor safety at an elevated temperature due to its low boiling point and be prone to generate gas during charge or cause swelling of the cell. In some embodiments, the electrolytes as disclosed herein are substantially free of any component that causes at least 5% change of volume after formation of battery . Typically, the formation of battery is completed after a few cycles at a controlled rate.

[0036] According to one aspect of the present disclosure, incorporation of other salts into electrolyte may increase the solubility of nitrate and enhance the final performance of the battery.

[0037] In some embodiments, the solvent comprises an ether with a formula (I):wherein R3ais selected from the group consisting of Ci-io alkyl, C3-10 cycloalkyl, C1-10 haloalkyl, C3- 10 halocycloalkyl, -[(C1-4 alkylene)-0-]x-(Ci-io alkyl), -[(C1-4 alkylene)-0-]x-(C3-io cycloalkyl), -[(Ci- 4 alkylene)-0-]x-(Ci-io haloalkyl) and -[(C1-4 alkylene)-0-]x-(C3-io halocycloalkyl),R4a, R5aand R6aare independently selected from the group consisting of H, F, C1-10 alkyl, C3-10 cycloalkyl, C1-10 haloalkyl, C3-10 halocycloalkyl, -0-(Ci-io alkyl), -0-(C3-io cycloalkyl), -0-(Ci-iohaloalkyl), -0-(C3-io halocycloalkyl), -[(C1-4 alkylene)-0-]y-(Ci-io alkyl), -[(C1-4 alkylene)-O-]y-(C3- locycloalkyl), -[(Ci-4 alkylene)-0-]y-(Ci-io haloalkyl), -[(Ci-4 alkylene)-0-]y-(C3-io halocycloalkyl), - O-[(Ci-4 alkylene)-0-]y-(Ci-io alkyl), -O-[(Ci-4 alkylene)-0-]y-(C3-io cycloalkyl), -O-[(Ci-4 alkylene)- O-]y-(C 1-10 haloalkyl), and -O-[(Ci-4 alkylene)-0-]y-(C3-io halocycloalkyl), and x and y are independently an integer in a range from 1 to 10.

[0038] In some embodiments, one of R4a, R5aand R6ain formula (I) is H. In some embodiments, two of R4a, R5aand R6ain formula (I) are H. In some embodiments, one of R4a, Raand R6ain formula (I) comprises at least one halogen element such as F, Cl, Br and I. In some embodiments, two of R4a, R?aand R6ain formula (I) comprise at least one halogen element such as F, Cl, Br and I.

[0039] In some embodiments, at least one of R4a, R5aand R6ain formula (I) are C1-10 alkyl, C1-10 haloalkyl, -0-(Ci-io alkyl), -0-(Ci-io haloalkyl), -[(C1-4 alkylene)-0-]y-(Ci-io alkyl), -[(C1-4 alkylene)- 0-]y-(Ci-io haloalkyl), -O-[(Ci-4 alkylene)-0-]y-(Ci-io alkyl), or -O-[(Ci-4 alkylene)-0-]y-(Ci-io haloalkyl).

[0040] In some embodiments, none of R3a, R4a, R3aand R6aincludes any halogen element.

[0041] In some embodiments, R3aincludes at least one halogen and at least one of R4a, R5aand R6aincludes at least one halogen.

[0042] In some embodiments, R4ais H, F, C1-10 alkyl, or C1-10 haloalkyl, R6ais H, F, C1-10 alkyl, or Ci-10 haloalkyl, R5ais -0-(Ci-io alkyl), -0-(Ci-io haloalkyl), -O-[(Ci-4 alkylene)-0-]y-(Ci-io alkyl), or -O-[(Ci-4 alkylene)-0-]y-(Ci io haloalkyl).

[0043] In some embodiments, R4ais H, R6ais H, R5ais -0-(Ci-io alkyl) or -0-(Ci-io haloalkyl).

[0044] In some embodiments, at least two of R4a, R5aand R6ain formula (I) are -0-(Ci-io alkyl), -O- (C1-10 haloalkyl), -[(C1-4 alkylene)-0-]y-(Ci-io alkyl), -[(C1-4 alkylene)-0-]y-(Ci-io haloalkyl), -O-[(Ci- 4 alkylene)-0-]y-(Ci-io alkyl), or -O-[(Ci-4 alkylene)-0-]y-(Ci-io haloalkyl).

[0045] In some embodiments, at least two of R4a, R5aand R6aare independently selected from the group consisting of -0-(Ci-io alkyl), -0-(Ci-io haloalkyl), -O-(Ci-4 alkylene)-0-(Ci-io alkyl), and -O- (C1-4 alkylene)-O-(Ci -10 haloalkyl).

[0046] In some embodiments, R6ain formula (I) can be H, F, alkyl such as methyl (Me) and ethyl, fluoroalkyl such as -CF3, -CHF2, and -CH2F, alkoxy such as -OMe, or haloalkoxy such as - OCH2CH2CI, -OCH2CHFCI, -OCH2CF3 and -OCH2CHF2.

[0047] In some embodiments, the electrolyte compositions include four or more electrolyte salts, a polymer, and a solvent. In other embodiments, the electrolyte compositions do not include a polymer.In some embodiments, the solvent comprises a non-halogenated ether. In some embodiments, the solvent comprises a non-halogenated ether and a halogenated ether such as fluorinated ether.

[0048] The electrolyte compositions of the disclosure include one or more non-limiting advantageous properties as follows. The electrolyte compositions of the disclosure can be stable (e.g., passing safety testing such as the safety tests described in the examples below) when comprised in an electrochemical device (e.g., a battery) that includes a lithium metal anode. The electrolyte compositions of the disclosure when comprised in an electrochemical device can have improved wetting capabilities (e.g., wetting speed, contact angles, or the like). The electrolyte compositions of the disclosure when comprised in an electrochemical device (e.g., a battery) can be thermally stable as none of the components of the electrolyte composition have a boiling point of less than 100 °C. The electrolyte compositions of the disclosure may be used to achieve safer, longer-life lithium batteries. The electrolyte compositions may exhibit better ionic conductivity. These properties may benefit charging / discharging rate performances. In some embodiments, the electrolyte composition further comprises a polymer.

[0049] In some embodiments, the non-halogenated ether can comprise 1,2-dimethoxy methane, 1,2- dimethoxy ethane, 1,2-diethoxy ethane, 1,1 -di ethoxy ethane, 1,1 -dipropoxy-ethane, 1,2-dipropoxy- ethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, or the like.

[0050] In some embodiments, the non-halogenated ether can comprise one or more of 1,2- dimethoxy ethane, 1,2-diethoxy ethane, 1,2-dibutoxy ethane, diethyl ether, dibutyl ether, di-tert-butyl ether, tert-butyl ethyl ether, zc / 7-butyl methyl ether, 1,3-dioxolane, 1,4-dioxane, di(propylene glycol) methyl ether. In some embodiments, the non-fluorinated ether comprises 1 ,2-diethoxyethane.

[0051] In some embodiments, the solvent is substantially free of 1,2-dimethoxy ethane (DME). As used herein, the term “substantially free of’ an ingredient(s) as provided throughout the disclosure is intended to mean that the composition or device contain less than about 0.1 wt% (percent by weight of the total weight of the composition or device(s)), or insignificant or negligible amounts of said ingredient(s) unless specifically indicated otherwise. In some embodiments, the compositions or devices of the present disclosure are substantially free of 1,2-dimethoxy ethane, meaning that the compositions or devices contain less than about 0.1 wt% 1,2-dimethoxy ethane.

[0052] In some embodiments, the halogenated ether is a fluorinated ether. In some embodiments, the fluorinated ether comprises one or more of bis(2,2,2-trifluoroethoxy)methane (BTFM), 1,1, 1,3, 3, 3- hexafluoro-2-( 1 , 1 , 1 ,3 , 3 ,3 -hexafluoropropan-2-yloxymethoxy)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, and 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), 1H, lH,5H-octafluoropentyl- 1 , 1 ,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), and tris(2,2,2-trifluoroethyl)orthoformate (TFEO). In some embodiments, the fluorinated ether is BTFM.

[0053] The solvent can comprise the non-halogenated ether in an amount in a range from 0.1 wt% to about 100 wt%. For example, the solvent comprises the non-fluorinated ether in an amount in a range from 0.1 wt% to about 99 wt%, from about 10 wt% to about 90 wt%, from about 20 wt% to about 80 wt%, from about 25 wt% to about 70 wt%, from about 25 wt% to about 45 wt%, or from about 50 wt% to about 80 wt%. In some embodiments, the solvent comprises the non-fluorinated ether in an amount in a range from about 25 wt% to about 45 wt% or from about 30 wt% to about 40 wt%.

[0054] The solvent can comprise the halogenated ether such as fluorinated ether in an amount in a range from 0.1 wt% to about 99 wt%. For example, the solvent comprises the halogenated ether in an amount in a range from 0.1 wt% to about 99 wt%, from about 10 wt% to about 90 wt%, from about 20 wt% to about 80 wt%, from about 25 wt% to about 75 wt%, or from about 55 wt% to about 75 wt%. In some embodiments, the solvent comprises the fluorinated ether in an amount in a range from about 55 wt% to about 75 wt% or from about 60 wt% to about 70 wt%.

[0055] In some embodiments, the non-halogenated ether and the halogenated ether are present in a weight ratio of 1 :20 to 20: 1 , 1 : 10 to 10: 1, 1 :5 to 10: 1, 1 :3 to 8: 1, or 1 : 1 to 3: 1 . In some embodiments, the non-halogenated ether and the halogenated ether are present in a weight ratio in a range from 1:3 to 8: 1 or from 1 : 1 to 3: 1.

[0056] In some embodiments, the solvent has a boiling point of at least 100 °C at 1 atm. In some embodiments, the solvent has a boiling point of at least 110 °C at 1 atm, at least 120 °C at 1 atm, at least 130 °C at 1 atm, or at least 140 °C at 1 atm. In some embodiments, the fluorinated ether and / or the non-fluorinated ether has a boiling point of at least 100 °C at 1 atm. The solvent can be present in the electrolyte composition in an amount of at least 15 wt%, based on the total weight of the electrolyte composition. For example, the solvent is present in the electrolyte composition in an amount of atleast 15 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 85 wt%, at least about 90 wt%, at least about 95 wt%, or at least about 98 wt%. For another example, the solvent is present in the electrolyte composition in a range from about 15 wt% to about 95 wt%, from about 25 wt% to 95 wt%, from about 50 wt% to 95 wt%, from about 75 wt% to about 90 wt%, from about 85 wt% to about 99.5 wt%, from about 85 wt% to about 99 wt%, from about 90 wt% to about 99 wt%, from about 30 wt% to about 60 wt%, or from about 40 wt% to about 55 wt%, based on the total weight of the electrolyte composition. In some embodiments, the solvent is present in the electrolyte composition in an amount in a range from 40 wt% to about 55 wt%, or from about 75 wt% to about 90 wt%, based on the total weight of the electrolyte composition.

[0057] The four or more electrolyte salts can be present in the electrolyte composition in an amount of about 5 wt% to about 85 wt%, based on the total weight of the electrolyte composition. For example, the four or more electrolyte salts can be present in the electrolyte composition in an amount of about 5 wt% to about 75 wt%, or about 15 wt% to about 75 wt%, or about 25 wt% to about 75 wt%, or about 30 wt% to about 70 wt%, or about 40 wt% to about 60 wt%, or about 15 wt% to about 50 wt%, or about 10 wt% to about 30 wt%, based on the total weight of the electrolyte composition. In some embodiments, the four or more electrolyte salts can be present in the electrolyte composition in an amount of about 40 wt% to about 60 wt%, based on the total weight of the electrolyte composition. In some embodiments, the four or more electrolyte salts are present in the electrolyte composition in an amount of about 10 wt% to about 30 wt%, based on the total weight of the electrolyte composition.

[0058] In some embodiments, the electrolyte of the present disclosure comprises four or more electrolyte salts, wherein the four or more electrolyte salts have a total concentration of at least 25 wt%, at least 30 wt%, or at least 35 wt%. In some embodiments, the electrolyte of the present disclosure comprises LiFSI with a concentration of at least 25 wt%, at least 30 wt%, or at least 35 wt%.

[0059] In some embodiments, the electrolyte of the present disclosure comprises a polymer in an amount of about 0.1 wt% to about 50 wt%, based on the total weight of the electrolyte composition. For example, the polymer is present in the electrolyte composition of the disclosure in an amount of about 0. 1 wt% to about 25 wt%, about 0.5 wt% to about 15 wt%, or about 0.5 wt% to about 2.5 wt%, based on the total weight of the electrolyte composition.

[0060] In some embodiments, the electrolyte compositions of the disclosure comprise the solvent in an amount of about 15 wt% to about 95 wt%; the four or more electrolyte salts in an amount of about5 wt% to about 85 wt%; and the polymer in an amount of about 0.1 wt% to about 50 wt%, based on the total weight of the electrolyte composition. In some embodiments, the electrolyte compositions of the disclosure comprise the solvent in an amount of about 40 wt% to about 60 wt%; the four or more electrolyte salts in an amount of about 40 wt% to about 60 wt%; and the polymer in an amount of about 0.5 wt% to about 2.5 wt%, based on the total weight of the electrolyte composition. In some embodiments, the electrolyte compositions of the disclosure comprise the solvent in an amount of about 70 wt% to about 90 wt%; the four or more electrolyte salts in an amount of about 10 wt% to about 30 wt%; and the polymer in an amount of about 0.5 wt% to about 2.5 wt%, based on the total weight of the electrolyte composition.[0061| Certain aspects include a polymer, a solvent, and four or more electrolyte salts. In some cases, the electrolyte composition may include a polymer that is crosslinked and has a heterogeneous polymer network obtained from a crosslinking reaction of a composition comprising one or more crosslinkers. In some embodiments, the polymer is synthesized from one or more crosslinkers, wherein at least one crosslinker has three or more polymerizable or crosslinkable terminals. In some embodiments, at least one of the one or more crosslinkers has three or more polymerizable or crosslinkable terminals.

[0062] In some embodiments, the electrolyte comprises a solvent, four or more salts, and a polymer, wherein the polymer is in situ polymerized from an electrolyte precursor comprising a solvent, four or more salts, and a crosslinker. In some embodiments, the in-situ polymerization is a thermal initiated polymerization such as free radical polymerization, polyaddition, and polycondensation. In some embodiments, the electrolyte precursor has a shelf-life of at least 3 days, at least 5 days, or at least 7 days to prevent undesired early curing.

[0063] In certain embodiments, the crosslinker has three or four polymerizable or crosslinkable arms, wherein each arm has a polymerizable or crosslinkable terminal covalently connected to a center. In some embodiments, the center can be an element of C, Si, N, P, B, or a cyclic ring. In some embodiments, each polymerizable or crosslinkable terminal is covalently connected to the center directly or via a spacer chain or group. In some embodiments, each arm is the same or different from each other.

[0064] In certain embodiments, the polymerizable or crosslinkable terminals are independently selected from the group consisting of C2-20 alkenyl, C2-20 alkynyl, epoxy, amino, hydroxyl, carboxylic acid, or any substituted form thereof.

[0065] In certain embodiments, the crosslinker with three or more polymerizable or crosslinkable terminals is a tri-acrylate, tetra-acrylate, modified tri-acrylate, modified tetra-acrylate, silane, siloxane or triazinane-trione (triazine-trione).

[0066] In certain embodiments, the crosslinker with three or more terminals has a formula selected from the group consisting of:wherein R.4 and Rs are independently selected from the group consisting ofwherein Ri, R2, R3, Re are each independently selected from the group consisting of hydrogen, methyl, ethyl, phenyl, methyl phenyl, benzyl, acryl, epoxy ethyl, isocyanate, cyclic carbonate, lactone, lactam, and vinyl, wherein n is an integer between 0 and 50,000 and * indicates a point of attachment.

[0067] In certain embodiments, modified tri-acrylates and tetra-acrylates include tri-acrylates and tetra-acrylates with substituted groups such as -CN, -SO2H, -CO2H, -CO2-, F, Cl, Br, or I.

[0068] In certain embodiments, the crosslinker has a formula of:

[0069] In certain embodiments, the crosslinker with three or more terminals is a silane or siloxane.

[0070] In some embodiments, one or more of the crosslinkers or the spacer chains or groups contain a structure including, but not limited to, -O-, -NRC-, -S-, -C(=O)-, -C(=O)O-, -C(=O)NRC-, -C(=O)S-, -OC(=O)O-, -NRCC(=O)O-, -NRCC(=O)NRC-, -S(=O)-, -S(=O)2-, -OS(=O)2-, -OS(=O)2O-, - NRCS(=O)2-, -NRCS(=O)2NRC-, -OS(=O)2NRC-, CI-6 alkylenyl, C2-6 alkenylenyl, C2-6 alkynylenyl, Ce- 14 arylenyl, 5- to 14-membered heteroaryl enyl, C3-10 cycloalkyl, or 3- to 10-membered heterocyclenyl, wherein the alkylenyl, alkenylenyl, alkynylenyl, arylenyl, heteroaryl enyl, cycloalkyl, or heterocyclenyl is optionally substituted with halogen, -CN, -NO2, C1-6 alkyl, C1-6 haloalkyl, C1-6 hydroxyalkyl, C1-6 aminoalkyl, C2-6 alkenyl, C2-6 alkynyl, Ce-14 aryl, 5- to 14-membered heteroaryl, C3-10 cycloalkyl, 3- to 10-membered heterocyclyl, -SRb, -S(=O)Ra, -S(=O)2Ra, -S(=O)2ORb, - S(=O)2NRcRd, -NRcRd, -NRcS(=O)2Ra, -NRcS(=O)2Ra, -NRcS(=O)2ORh, -NRcS(=O)2NRcRd, - NRbC(=O)NRcRd, -NRbC(=O)Ra, -NRbC(=O)ORb, -ORb, -OS(=O)2Ra, -OS(=O)2ORb, - OS(=O)2NRcRd, -OC(=O)Ra, -OC(=O)ORb, -OC(=O)NRcRd, -C(=O)Ra, -C(=O)ORb, or - C(=O)NRcRd; wherein Ra, Rb, Rc, and Rdare independently C1-6 alkyl, C1-6 haloalkyl, Ci-6 hydroxyalkyl, C1-6 aminoalkyl, C2-6 alkenyl, C2-6 alkynyl, C3-10 cycloalkyl, 3- to 10-membered heterocyclyl, Ce-14 aryl, or 5- to 14-membered heteroaryl, wherein the alkyl, haloalkyl, hydroxyalkyl, aminoalkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more oxo, halogen, -CN, -OH, -OMe, -NH2, -C(=O)Me, -C(=O)OH, -C(=O)OMe, C1-6 alkyl, or C1-6 haloalkyl.

[0071] In some embodiments, Rcand Rd, together with the hetero atom (such as N, O, S, P), form a 3- to 10-membered heterocyclyl, wherein the heterocyclyl is optionally substituted with one or more oxo, halogen, -CN, -OH, -OMe, -NH2, -C(=O)Me, -C(=O)OH, -C(=O)OMe, Ci-e alkyl, or C1-6 haloalkyl.

[0072] In certain embodiments, one of the crosslinkers or the spacer chains or groups comprise a structure of -XC(=O)CR3=C(R4)2, wherein X is independently O or NRe, Reis independently H or Ci- 6 alkyl, and each R3and R4is independently H or Ci-6 alkyl.

[0073] In certain embodiments, one of the crosslinkers comprises one or more functional groups including without limitation:a

[0074] In certain embodiments, the crosslinker with one or more functional groups includes without limitation:

[0075] In some embodiments, the crosslinker with one or more functional groups is a monomer for ring opening polymerization and has a formular as follows:and any substituted form thereof, wherein x is an integer ranging from 1 to 1000.

[0076] In some embodiments, the monomer for ring opening polymerization includes:

[0077] In some embodiments, the monomer for ring opening polymerization comprises an unsubstituted or substituted oxirane ring, oxetane ring, furan ring, aziridine ring, and azetidine ring.

[0078] In addition, certain embodiments are directed to compositions for use with polymer solid electrolytes, batteries, or other electrochemical devices including same, and methods for producing same. In some cases, the incorporation of vinyl and / or allyl functional groups with UV crosslinking or thermal crosslinking can be used to improve various electrochemical performance, especially whenthe crosslinker has polymerizable or crosslinkable terminals, such as vinyl and allyl, in at least three directions of the chemical structure of the crosslinker (i.e. the crosslinker has three crosslinkable terminals), the electrochemical performance can be improved more obviously.

[0079] In one aspect, the present disclosure is generally directed to an electrochemical cell, such as a battery, including an electrolyte composition as disclosed herein. The electrochemical cell may include an anode, a cathode, and / or a separator. Many of these are available commercially. In some embodiments, the electrolyte composition of the disclosure may be used as the electrolyte of the electrochemical cell, alone and / or in combination with other electrolyte materials.

[0080] In addition, in one set of embodiments, the terminals or groups such as vinyl and / or allyl may be crosslinked together. For example, such functional groups may be crosslinked using UV light, at an elevated temperature (e.g., between 40 °C and 100 °C), in the presence of an initiator, or other methods including those described herein. In some cases, the incorporation of three or more crosslinkable terminals leads to a disorganized or disordered network, resulting in improved electrochemical performances, or the like, such as relatively high ionic conductivities and decomposition voltages.

[0081] Provided herein is an electrochemical device comprising the electrolyte composition as described herein.

[0082] In some embodiments, the electrochemical device is anode-free or comprises a Li anode.

[0083] In some embodiments, the anode is a carbon anode, Li anode, Si anode, Alloy anode, Li4Ti50i2, or made from conversion anode materials. In some embodiments, the carbon anode comprises graphite, soft carbon, hard carbon, or combinations of thereof. In some embodiments, the Li anode comprises Li metal foil, Li alloy, Li metal or Li alloy on Cu, Ni, or stainless steel. In some embodiments, the Si anode comprises Si, Si / Carbon composite, SiOx (0<x<2), SiOx (0<x<2) / carbon composite or a combination thereof. In some embodiments, the alloy anode comprises Sn, SnCh, Sb, Al, Mg, Bi, In, As, Zn, Ga, B, or a combination thereof. In some embodiments, the conversion anode materials comprise MaXb, M is Mn, Fe, Co, Ni, or Cu, X is O, S, Se, F, N, or P, a and b are respectively 1 to 4. In some embodiments, the anode is Li metal foil or Li metal on Cu, Ni, or stainless steel.

[0084] In some embodiments, the electrochemical device comprises a cathode. In some embodiments, the cathode has an average voltage of at least 3.5 V vs Li metal. In some embodiments, the cathode comprises lithium metal oxide. In some embodiments, the cathode comprises an active material including one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, lithium manganese oxide, lithium cobalt oxide, and lithium iron phosphate.

[0085] In some embodiments, it is challenging for a battery with an anode layer with a relatively lower thickness to achieve a good cycling performance. In some embodiments, the anode layer of the battery as disclosed herein has a thickness of no greater than 50 pm, no greater than 40 pm, no greater than 30 pm, no greater than 20 pm, no greater than 10 pm, no greater than 7 pm, or no greater than 5 pm.

[0086] In some embodiments, the electrochemical device disclosed herein, such as lithium-ion battery (LIB), lithium metal battery and lithium metal solid state battery, passes an overcharge test, wherein the electrochemical device is at 100% state-of-charge and is overcharged at 3 mA / cm2charge rate for 1 hour or when 8.5V is reached with a European Council for Automotive Research (EUCAR) hazard level of 4 or below.

[0087] In some embodiments, the electrochemical device, such as lithium metal battery and lithium metal solid state battery, passes 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 EUCAR hazard level of 4 or below.

[0088] In some embodiments, the electrochemical device maintains a specific capacity of at least 160 mAh / g for at least 200 asymmetric cycles, or at least 300 asymmetric cycles, or at least 400 asymmetric cycles, wherein the charge current density is 1 mA / cm2and the discharge current density is 3 mA / cm2.

[0089] In some embodiments, the electrochemical device maintains a specific capacity of at least 140 mAh / g for at least 120 symmetric cycles, or at least 150 symmetric cycles, or at least 180 symmetric cycles, wherein the charge current density and discharge current density are 1 mA / cm2.

[0090] In some embodiments, the electrochemical device can be fast charged with a charge current density of at least about 10 mA / cm2, at least about 15 mA / cm2, at least about 18 mA / cm2, or about 10 mA / cm2to about 18 mA / cm2.

[0091] Also provided herein are electrochemical devices comprising an anode, a cathode, and an electrolyte composition of the disclosure, wherein the electrolyte composition of the disclosure comprises four or more electrolyte salts and a solvent; wherein the electrochemical cell can be fast charged with a current density in a range of about 10.5 mA / cm2to about 16.5 mA / cm2. In some embodiments, the electrochemical device is a lithium metal battery or lithium metal solid state battery. In some embodiments, the solvent comprises a non-halogenated ether. In some embodiments, the solvent comprises a non-halogenated ether and a halogenated ether.

[0092] In some embodiments, the electrolyte composition of the disclosure may further include an additive. In some embodiments, the additive may provide improved processability, and / or better cycle performance.

[0093] In some embodiments, the additive can be present at a weight percentage of about 1 wt% to about 10 wt% or about 0.01 wt% to about 5 wt%, based on a total weight of the electrolyte composition.

[0094] In some embodiments, the electrolyte composition may further include an initiator. Specific non-limiting examples of initiators include 2,2’-azobis(2-methylpropionitrile), benzoyl peroxide, cumene hydroperoxide, dicumyl peroxide, ter-butyl hydroperoxide, di -tert-butyl peroxide, 2,2’- azobis[2-(2-imidazoline-2-yl)propane] dihydrochloride, ammonium persulfate, anisoin, anthraquinone, benzophenone, benzoin methyl ether, 2-isopropylthioxanthone, 9,10- phenanthrenequinone, 3 ’ -hydroxyacetophenone, 3,3 ’ ,4,4’ -benzophenonetetreacarboxylic dianhydride, 2-benzoylbenzoic acid, (±)-camphorquinone, 2-ethylanthraquinone, 2- methylbenzophenone, 4-hydroxybenzophenone, 2-hydroxy-2-methylpropiophenone, benzoin isobutyl ether, 4,4’-bis(dimethylamino)benzophenone, 4,4’ -dihydroxybenzophenone, 4-benzoyl 4’- methyldiphenyl sulfide, ferrocene, dibenzosuberenone, benzoin ethyl ether, benzil, methyl benzoylformate, 4-benzoylbenzoic acid, or others alike. In some cases, the initiator has a weight fraction (weight percentage) between 0.01 wt% and 5 wt%, or other suitable mole fractions to initiate polymerization or crosslinking, based on a total weight of the polymer solid electrolyte. In some embodiments, the weight fraction is no more than 5.0 wt%, no more than 4.0 wt%, no more than 3.0 wt%, no more than 2.0 wt%, or no more than 1.0 wt%. In some embodiments, the weight fraction is no more than 1.0 wt%, no more than 0.8 wt%, no more than 0.6 wt%, no more than 0.4 wt%, no more than 0.2 wt%, no more than 0.1 wt%, or no more than 0.05 wt%.

[0095] Certain aspects of the disclosure are generally directed to systems and methods for producing any of the electrolyte compositions discussed herein. For example, a polymer may be produced by reacting various crosslinkers together.

[0096] The present disclosure generally relates to a device with the electrolyte compositions disclosed herein. The device may be a battery, a lithium metal battery or a lithium metal solid-state battery. The battery may be configured for applications such as portable applications, transportation applications, stationary energy storage applications, and the like. Non-limiting examples of the ion-conducing batteries include lithium-ion conducting batteries, and the like. The device may also be a battery comprising one or more lithium ions electrochemical cells.

[0097] In various examples, a battery includes an electrolyte composition of the present disclosure, an anode, and a cathode with a cathode active material. In some embodiments, the battery is a lithium metal battery, wherein the anode comprises lithium metal or lithium alloy.

[0098] In some embodiments, the electrolyte as described herein exhibits an ionic conductivity of at least 1 .00 mS / cm, at least 1 .50 mS / cm, at least 2.00 mS / cm, at least 2.50 mS / cm, at least 3.00 mS / cm, at least 3.50 mS / cm, at least 4.00 mS / cm, at least 4.50 mS / cm, at least 5.00 mS / cm, at least 5.50 mS / cm, or at least 6.00 mS / cm at 25 °C.

[0099] In some embodiments, the electrochemical device such as lithium metal battery has a capacity retention of at least 95.0%, at least 96.0%, at least 97.0%, at least 98.0%, at least 98.5%, at least 99.0% at least 99.2%, at least 99.5% or at least 99.7% after 150 cycles using a charge and discharge current density of 1 mA / cm2(0.33C) at 25°C.

[0100] In some embodiments, the electrochemical device has a discharge specific capacity of at least 160 mAh / g, at least 165 mAh / g, at least 170 mAh / g, at least 175 mAh / g, or at least 180 mAh / g, after 150 cycles using a charge and discharge current density of 1 mA / cm2(0.33C) at 25°C.

[0101] In some embodiments, the electrochemical device such as lithium metal battery exhibits an average columbic efficiency (CE) of at least 99.00%, at least 99.20%, at least 99.40%, at least 99.50%, at least 99.60, at least 99.70, at least 99.80, at least 99.85%, or at least 99.90% for the first 150 cycles at a charge and discharge current density of 1 mA / cm2(0.33C) at 25°C.

[0102] Without wishing to be bound by any theory, the improved cycling performance may be ascribed to formation of better solid electrolyte interphase (SEI) and improved diffusivity due to 4 and more salts in the electrolyte.

[0103] Some crosslinkers, electrolyte salts, additives and other materials as described in WO 2020096632 Al and US publication no. 20200144665 Al and 20200144667 Al are incorporated herein by reference in its entirety.

[0104] Although the disclosed teachings have been described with reference to various applications, methods, compounds, compositions, and materials, it will be appreciated that various changes and modifications to them may be made without departing from the teachings herein. The following examples are provided to better illustrate the disclosed teachings and are not intended to limit the scope of the teachings presented herein. While the present teachings have been described in terms of these exemplary embodiments, the skilled artisan will readily understand that 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 of this disclosure.EXAMPLESExample 1Preparation of electrolyte comprising multiple lithium salts

[0105] A solvent comprising 1,2-di ethoxy ethane (DEE), and bis(2,2,2-trifluoroethoxy)methane (BTFM) was prepared. Multiple salts including lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorophosphate (LiDFP) were added into the solvent. Lithium nitrate (LiNC ) was added after other salts were fully dissolved, forming a number of homogenous solutions as electrolyte examples 1-1, 1-2, 1-3, and 1-4 shown in Table 1.Table 1 Electrolyte compositions

[0106] 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 electrolytes as prepared. The ionic conductivity of the electrolyte was calculated based on the bulk resistance obtained by electrochemical impedance spectroscopy (EIS) measurements at 25 °C.

[0107] Comparative example 1 was prepared according to reference [Nat Commun 14, 440 (2023)], wherein the solvent is 1,2-dimethoxy ethane (DME) without any co-solvent. Coin cells using comparative example 1 as electrolyte all shorted during CE test and resulted in low average CE with large deviation. The standard deviation is calculated based on 3 duplicate cells. On the contrary, coin cells using example 1-1, example 1-2, example 1-3 and example 1-4 as electrolyte all showed high average CE with small deviation, indicating significantly improved Li metal stability. The total salt concentration (wt%) is low in comparative example 1, which contributed to its high ionic conductivity of 6.04 mS / cm. However, the high ionic conductivity of comparative example 1 is achieved bysacrificing Li metal stability. Examples 1-1, 1-2, 1-3, and 1-4 all show high ionic conductivity without sacrificing Li metal stability.Table 2 Ionic conductivity of electrolytes and average CE of batteries comprising the electrolytesa: Average CE is total Li stripping cycle capacity divided by total Li plating cycle capacity using Aurbach CE protocol with a current density of 1.0 mA / cm2, a capacity of 3.0 mAh / cm2, and a total of 50 stripping / plating cycles. [Adv. Energy Mater. 2017, 1702097],Example 2

[0108] An electrolyte comprising a polymer was prepared by mixing Example 1-1 as base electrolyte, pentaerythritol tetraacrylate (PETA) as monomer, and AIBN as initiator followed by polymerization at 65 °C. The composition of the polymer electrolyte precursor is shown in Table 3.Table 3 Electrolyte precursor compositions before polymerization

[0109] A multi-layer pouch cell comprising Li metal as anode, microporous membrane as separator, NMC811 as cathode, and polymer electrolyte example 2-1 as electrolyte was cycled between 2.8 V to 4.25 V at 25 °C using a current density of 1.0 mA / cm2(0.33C) under an external pressure in a range from 0.5 MPa to 5.0 MPa. The specific discharge capacity, discharge capacity retention, and CE are shown in Fig. 1, Fig. 2, and Fig. 3, respectively. The initial specific discharge capacity is 182 mAh / g. The cell showed no capacity loss after 200 cycles. As shown in Fig. 2, the cycle life is 268 cycles, which is the number of cycles before the cell reaches 80% discharge capacity retention. As shown in Fig. 3, the coulombic efficiency (CE) is high and consistently greater than 99%.Example 3

[0110] Electrolytes with compositions in Table 4 were prepared and tested similar to Example 1 except AgNCh was used as nitrate salt instead of LiNCh. As shown in Table 5, the electrolyte example 3-1 exhibited an ionic conductivity of 4.48 mS / cm and a battery comprising the electrolyte exhibited an average CE of 99.26%.Table 4 Electrolyte compositionsTable 5 Ionic conductivity of electrolytes and average CE of batteries comprising the electrolytesExample 4

[0111] Electrolytes with compositions in Table 6 were prepared and tested similar to Example 1 except LiCICU was used instead of LiDFP. As shown in Table 7, examples 4-1, 4-2, and 4-3 show high ionic conductivity and batteries comprising the electrolytes show high average CE.Table 6 Electrolyte compositionsTable 7 Ionic conductivity of electrolytes and average CE of batteries comprising the electrolytesExample 5

[0112] Electrolytes with compositions in Table 8 were prepared and tested similar to Example 1 except tetraethylammonium nitrate (TEAN) was used instead of LiNCh. As shown in Table 9, examples 5-1 and 5-2 show high ionic conductivity and batteries comprising the electrolytes show high average CE.Table 8 Electrolyte compositionsTable 9 Ionic conductivity of electrolytes and average CE of batteries comprising the electrolytesASPECTS

[0113] In a first aspect of the disclosure, an electrolyte for an electrochemical device such as lithium metal battery comprises four or more salts dissolved in a nonaqueous solvent, wherein the four or more salts are chemically stable with each other in the presence of the solvent, and the electrolyte is stable in presence of lithium metal.

[0114] In a second aspect according to the first aspect, the electrolyte is substantially free of PF 6".

[0115] In a third aspect according to the first or second aspect, two of the four or more salts are lithium bis(fluorosulfonyl)imide (LiFSI) and nitrate salt. In some embodiments, the nitrate salt comprises at least one selected from the group consisting of lithium nitrate (LiNC ), silver nitrate (AgNCh), sodium nitrate, potassium nitrate, zinc nitrate, magnesium nitrate, aluminum nitrate, and calcium nitrate.

[0116] In a fourth aspect according to the third aspect, the nitrate salt comprises at least one cation selected from the group consisting of tetraalkylammonium, tetraalkylphosphonium, l-alkyl-3- alkylimidazolium, N-alkyl-N-alkylpyrrolidinium, N-alkyl-N-alkylpiperidinium, and N-alkyl-N- alkylazepanium.

[0117] In a fifth aspect according to the third aspect, the four or more salts comprise at least one salt that can increase the solubility of the nitrate salt in the solvent.

[0118] In a sixth aspect according to the first aspect, the four or more salts comprise LiFSI, a nitrate salt and at least two salts selected from the group consisting of lithium perchlorate (LiClCh), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCFsSOs), lithium bisperfluoro- ethysulfonylimide (LiBETI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiBF2C2O4, LiDFOB), lithium fluorophosphate (Li2PO3F), lithium difluorophosphate (LiDFP), lithium difluoro(bisoxalato)phosphate (LiC4POsF2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)3), lithium 4,5-dicyano-2- trifluoromethylimidazole (LiTDI), lithium acetate, and lithium trifluoromethyl acetate.

[0119] In seventh aspect according to any of the first through sixth aspects, the nonaqueous solvent comprises a non-halogenated ether and a halogenated ether. In some embodiments, the nonaqueous solvent comprises a non-halogenated ether.

[0120] In an eighth aspect according to any preceding aspect, the solvent is substantially free of carbonate solvents.

[0121] In a nineth aspect according to any preceding aspect, the solvent is substantially free of compounds that can generate a considerable amount of gas and cause more than 10% swelling of the battery during charging or discharge of the lithium metal battery. In some embodiments, the solvent is substantially free of 1,2-dimethoxy ethane (DME).

[0122] In a tenth aspect according to any preceding aspect, the electrolyte is stable in the presence of high voltage cathode that has an average voltage of at least 3.5 V vs Li metal, wherein the cathode comprises at least one selected from lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium cobalt oxide.

[0123] In an eleventh aspect according to any preceding aspect, the nonaqueous solvent has a boiling point of at least 100 °C at 1 atm.

[0124] In a twelfth aspect according to any preceding aspect, the four or more salts have a total concentration of at least 2.0 mol / L or at least 25 wt%. In some embodiments, LiFSI is one of the four or more salts and has a molar concentration higher than all other lithium salts.

[0125] In some embodiments, LiFSI is one of the four or more salts and has a concentration of at least 1.5 mol / L or 20 wt%.

[0126] In a thirteenth aspect according to any preceding aspect, the electrolyte further comprises a polymer with a weight percentage in a range from 0.1 wt% to 50 wt% in the electrolyte, wherein the polymer is in situ polymerized from a monomer after mixing the four or more salts, the solvent, themonomer, and an initiator into a mixture and injecting the mixture into an assembly comprising an anode, a separator and a cathode. In some embodiments, the monomer is selected from the group consisting of 2, 2, 3, 3 -tetrafluorobutane- 1,4-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- 10000), triethylene glycol di methacryl ate (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 tri methacryl ate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, and a combination thereof.

[0127] In a fourteenth aspect, the present disclosure provides an electrochemical device comprising an anode and the electrolyte according to any preceding aspect.

[0128] In some embodiments, the anode comprises an anode active material comprising at least one selected from the group consisting of lithium metal and lithium alloy.

[0129] In a fifteenth aspect according to the fourteenth aspect, the electrochemical device exhibits an initial specific capacity of at least 165 mAh / g and a capacity retention of at least 95.0% after 150 cycles at a current density of 1 mA / cm2(0.33C) at 25°C.

[0130] In some embodiments, the electrochemical device exhibits a discharge specific capacity of at least 160 mAh / g after 150 cycles at a current density of 1 mA / cm2(0.33C) at 25°C. In some embodiments, the electrochemical device exhibits an average columbic efficiency (CE) of at least 99.00% for the first 100 cycles at a current density of 1 mA / cm2(0.33C) at 25°C.

[0131] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0132] All transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively.

[0133] 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 alternative to the specific embodiments described herein are also within the scope of this disclosure.

Claims

We claim:

1. An electrolyte of a lithium metal battery, comprising:• four or more salts dissolved in a nonaqueous solvent, wherein the four or more salts are chemically stable with each other in the presence of the nonaqueous solvent, and the electrolyte is stable in the presence of lithium metal.

2. The electrolyte of claim 1, wherein the electrolyte is substantially free of PFe’.

3. The electrolyte of claim 1, wherein two of the four or more salts are lithium bis(fluorosulfonyl)imide (LiFSI) and nitrate salt.

4. The electrolyte of claim 3, wherein the nitrate salt comprises a cation selected from the group consisting of tetraalkylammonium, tetraalkylphosphonium, l-alkyl-3-alkylimidazolium, N- alkyl-N-alkylpyrrolidinium, N-alkyl-N-alkylpiperidinium, and N-alkyl-N-alkylazepanium.

5. The electrolyte of claim 3, wherein four or more salts comprise at least one salt that can increase the solubility of the nitrate salt in the nonaqueous solvent.

6. The electrolyte of claim 1, wherein the four or more salts comprise LiFSI, a nitrate salt and at least two salts selected from the group consisting of lithium perchlorate (LiCICL), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bi sperfluoro-ethy sulfonylimide (LiBETI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFsSO2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiBF2C2O4, LiDFOB), lithium fluorophosphate (Li2PO3F), lithium difluorophosphate (LiDFP), lithium difluoro(bisoxalato)phosphate (LiC4POsF2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3862)3), lithium 4,5-dicyano-2-trifluoromethylimidazole (LiTDI), lithium acetate, and lithium trifluoromethyl acetate.

7. The method of claim 1, wherein the solvent comprises a non-halogenated ether and a halogenated ether.

8. The electrolyte of claim 1, wherein the solvent is substantially free of carbonate solvents.

9. The electrolyte of claim 1, wherein the solvent is substantially free of compounds that can generate a considerable amount of gas and cause more than 10% swelling of the battery during charging or discharging of the lithium metal battery.

10. The electrolyte of claim 1, wherein the electrolyte is stable in the presence of high voltage cathode that has an average voltage of at least 3.5 V vs Li metal, wherein the cathode comprises at least one selected from lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium cobalt oxide.

11. The electrolyte of claim 1, wherein the solvent has a boiling point of at least 100 °C at 1 atm.

12. The electrolyte of claim 1, wherein the four or more salts have a total concentration of at least 2.0 mol / L or at least 25 wt% in the electrolyte.

13. The electrolyte of claim 1, further comprising a polymer with a weight percentage in a range from 0. 1 wt% to 50.0 wt% in the electrolyte, wherein the polymer is in situ polymerized from a monomer after mixing with the four or more salts, the solvent and an initiator into a mixture and injecting the mixture into an assembly comprising an anode, a separator and a cathode.

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

15. The electrochemical device of claim 14, wherein the electrochemical device exhibits an initial specific capacity of at least 165 mAh / g and a capacity retention of at least 95.0% after 150 cycles at a current density of 1 mA / cm2(0.33C) at 25°C.

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