Asymmetric ether solvents for lithium-metal batteries

Abstract

Asymmetric non-fluorinated ethers (e.g.. 1,2-methoxy ethoxy ethan(EME), 1-methoxy-2-propoxy ethane (MPE), 1-methoxy-2-isopropoxy ethane (MiPE)). and fluorinated EME solvents exhibit high performance for lithium-metal batteries. Among fluorinated EME-based solvents are 1- methoxy-2-(2-fluoroethoxy) ethane (F1EME), 1-methoxy -2-(2,2-difluoroethoxy) ethane (F2EME), and l-methoxy-2-(2,2,2-trifluoroethoxy) ethane (F3EME). Electrolyte compositions obtained by mixing lithium bis(fluorosulfonyl)imide (LiFSI) with the aforementioned solvents enable high coulombic efficiency and lithium metal compatibility. Cycling with diverse electrodes (NMC811, LFP, NMC532, Ni95, SPAN (sulfurized polyacrylonitrile), and Si) reveals high lithium metal compatibility, oxidative stability, rate performance in high-voltage full cells, and excellent cyclability.

Description

Atty. Dkt. No. 102354-0797S24-137 PCTASYMMETRIC ETHER SOLVENTS FOR LITHIUM-METAL BATTERIESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is based on and claims priority to U.S. Provisional Patent Application No. 63 / 689,564 filed August 30, 2024, the contents of which are incorporated herein by reference in their entirety.FIELD

[0002] The present disclosure relates generally to energy storage and more particularly to ether solvents for lithium metal batteries.STATEMENT OF GOVERNMENT SPONSORED RESEARCH

[0003] This invention was made with Government support under contract DE-AC02-76SF00515 awarded by the Department of Energy. The Government has certain rights in the invention.BACKGROUND

[0004] Rechargeable batteries employing metallic lithium anodes rely heavily on ether-based liquid electrolytes because ethers are chemically compatible with Li° and can form a pliable, ion-conductive solid-electrolyte interphase (SEI). However, the low oxidative stability and high volatility / flammability of conventional ethers (e.g., dimethoxyethane (DME) and 1,3-dioxolane (DOL)) limit their use with high-energy, high-voltage cathodes and raise safety concerns for large cells. Moreover, uncontrolled solvation of lithium ions in dilute ether electrolytes can exacerbate dendritic growth and parasitic reactions, eroding Coulombic efficiency and cycle life.

[0005] Consequently, there is great interest in next-generation ether-based solvents and related electrolyte formulations that exhibit wider electrochemical stability windows, possess reduced vapor pressure and flammability, and suppress dendrite growth while maintaining high ionic conductivity. Previous patent applications drawn to this subject matter disclose fluorinated dimethoxybutane (FDMB) (see WIPO Publ. No. WO 2021 / 086854), nonfluorinated ethylene1S24-137 PCT I. Choi et al. Atty. Dkt 102354-0797 4902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTglycols and acetals, and fluorinated diethoxyethane (FDEE) (see WIPO Publ. No. WO 2023 / 069740), and fluorinated acetals (FDEM) (see WIPO Publ. No. WO2023 / 215607), the entire contents of which are incorporated herein by reference. The compounds and electrolyte formulations disclosed therein significantly advanced the state of the art in improving electrolyte compatibility with lithium metal batteries. Nevertheless, improved solvents and electrolyte formulations for Li metal batteries would be highly advantageous.SUMMARY

[0006] In one aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to an electrolyte composition for a lithium-metal battery, the electrolyte composition comprising:a lithium compound; anda solvent selected from:an asymmetric non-fluorinated ether selected from 1,2-methoxy ethoxy ethane (EME), 1 -methoxy -2-propoxy ethane (MPE), l-methoxy-2-isopropoxy ethane (MiPE), and combinations thereof;a fluorinated asymmetric ether;a fluorinated asymmetric acetal; andcombinations thereof.

[0007] In some embodiments, the fluorinated asymmetric ether comprises a fluorinated EME selected from: l-methoxy-2-(2-fluoroethoxy) ethane (F1EME); 1 -methoxy -2-(2, 2-difluoroethoxy) ethane (F2EME); l-methoxy-2-(2,2,2-trifluoroethoxy) ethane (F3EME); and combinations thereof. In some embodiments, the fluorinated EME comprises F3EME or EME. In some embodiments, the solvent comprises F3EME.

[0008] In some embodiments, the solvent comprises MiPE, MPE, EME, or a combination thereof. In some embodiments, the solvent comprises EME.24902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0009] In some embodiments, the lithium compound comprises LiFSI. In some embodiments, the lithium compound is present at a concentration of IM to 5M. In some embodiments, the lithium compound is present at a concentration of 1.5 M to 2.5 M.

[0010] In some embodiments, the electrolyte composition further comprises an electrolyte additive. In some embodiments, the electrolyte additive comprises LiDFP. In some embodiments, the electrolyte additive is present in the electrolyte composition at a concentration of about 0.5 wt.% to 5 wt.%.

[0011] In another aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to a battery, comprising:a cathode current collector:a cathode in contact with the current collector;an anode opposite the cathode, wherein the anode comprises lithium metal;an anode current collector in contact with the anode; andthe electrolyte composition according to any of the embodiments disclosed herein between the anode and the cathode.

[0012] In some embodiments, the battery further comprises a separator between the anode and the cathode.

[0013] In some embodiments, the solvent comprises F3EME. In some embodiments, the lithium compound comprises LiFSI. In some embodiments, the lithium compound is present in the electrolyte composition at a concentration of 1 M to 4 M. In some embodiments, the lithium compound is present in the electrolyte composition at a concentration of 1.5 M to 2.5 M. In some embodiments, the electrolyte composition further comprises LiDFP.

[0014] In another aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to a method of making a battery, the method comprising:combining a lithium compound and a solvent to produce the electrolyte composition according to any of the embodiments disclosed herein;contacting a cathode with a cathode current collector;34902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTcontacting an anode comprising Li metal with an anode current collector, the anode being opposite the cathode; anddisposing the electrolyte composition between the cathode and the anode to obtain the battery.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other aspects and features of the present embodiments will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures, wherein:

[0016] FIG. 1 is a reaction scheme showing synthesis of F1EME.

[0017] FIG. 2 shows(top),13C (middle), and19F (bottom) NMR spectra of F1EME in CDCh.

[0018] FIG.3 is a reaction scheme showing synthesis of F2EME.

[0019] FIG. 4 shows(top),13C (middle), and19F (bottom) NMR spectra of F2EME in CDCh.

[0020] FIG. 5 is a reaction scheme showing synthesis of F1EME

[0021] FIG. 6 shows(top),13C (middle), and19F (bottom) NMR spectra of F3EME in CDCh.

[0022] FIG. 7 shows reaction schemes for syntheses of EME, MPE, and MiPE.

[0023] FIG. 8 is a 'HNMR spectrum of EME in CDCh.

[0024] FIG. 9 is aXH NMR spectrum of MPE in DMSO.

[0025] FIG. 10 is a 'H NMR spectrum of MiPE in DMSO.

[0026] FIG. 11 shows relative solvation free energy (left) and Raman spectra (right) for IM LiFSI in DME, MEE, MPE, MiPE, and DEE.44902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0027] FIG. 12 shows ionic conductivity values for IM LiFSI in DME, MEE, MPE, MiPE, and DEE

[0028] FIG. 13 shows Li||Cu long cycling coulombic efficiency (CE) test results for IM LiFSI in DME, MEE, MPE, MiPE, and DEE, with current density of 0.5 mA and capacity of 1 mAh.

[0029] FIG. 14 shows two replicative Li||Cu CE tests with electrolyte using (a) symmetric solvent (DME, DEE) and (b) asymmetric solvent (EME, MPE, MiPE).

[0030] FIG. 15 is a schematic outlining advantages of using EME solvent compared to DME or DEE based on Raman spectroscopy (left) and ionic conductivity (right).

[0031] FIG. 16 shows Li||Cu long cycling CE test results with different current densities (0.1, 0.5, 2 mA, left to right) and 1 mAh capacity.

[0032] FIG. 17 shows Li||Cu CE difference between EME and DEE-based electrolytes for different current densities.

[0033] FIG. 18 shows Li ||Cu long cycling test results using different solvent-based localized high-concentration electrolyte (LHCE) (for DME, EME DEE).

[0034] FIG. 19 shows ionic conductivity of LiFSI in different electrolytes (EME, F1EME, F2EME, F3EME) at various salt concentrations with CELGARD™ 2325 separator.

[0035] FIG. 20 shows relative solvation free energy measurement (left) and Raman spectroscopy (right) of 2 M LiFSI in EME, F1EME, F2EME, and F3EME. The ratio between SSIP, CIP, AGG is shown in the figure, calculated from deconvoluting the Raman specta.

[0036] FIG. 21 shows Li ||Cu CE determined using the Aurbach method for 2 M LiFSI in EME, F1EME, F2EME, and F3EME (summary of 3 repeated cells shown in the figure).

[0037] FIG. 22 shows Li||Cu long cycling CE test results using 2 M LiFSI in EME, F1EME, F2EME, and F3EME (left) and a zoomed in plot of the CE vs. cycle number plot from 0 to 20 cycles (to achieve 99.0% CE) is shown on the right.54902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0038] FIG. 23 shows a voltage profile of Li||Li symmetric cells cycling with 4 electrolytes (2 M LiFSI in EME, Fl EME, F2EME, and F3EME). Panel (a) shows Li||Li cycling voltage profiles with a current density of 1 mA- cm’2and a cut-off capacity of 1 mAh cm’2. Panel (b) shows a zoomed-in plot of panel (a) from 170-180 cycles. Overpotential of each electrolyte is shown in panel (c), which is a Li||Li cycling voltage profile with varying current densities. The current is 1, 4, 6, 8, and 10 mA, and the capacity is 3 mAh.

[0039] FIG. 24 shows linear sweep voltammetry (LSV) of Li|| Al (left) and Li| |Pt (right) showing increased oxidative stability with higher degree of fluorination.

[0040] FIG. 25 shows discharge capacity and CE of Li||NMC811 coin cells with 50-pm thick Li anode and high-loading NMC811 cathode using 2 M LiFSI in EME, F1EME, F2EME, and F3EME. Cells were cycled between 2.8 V and 4.4 V at 0.8 mA -m’2charge and 1.3 mA cm’2discharge current density. Two replicated cells are shown.

[0041] FIG. 26 shows discharge capacity and CE of Li||NMC811 coin cells with 50-pm thick Li anode and high-loading NMC811 cathode using 1.2 M LiFSI in F5DEE, 2 M LiFSI in F3EME, and 2 M LiFSI in F3EME with 1 wt.% LiDFP additive. Cells were cycled between 2.8 V and 4.4 V at 2 mA- cm’2charge and 4 mA- cm’2discharge current density. Two replicated cells are shown.

[0042] FIG. 27 shows charge / discharge curves of cycle 3, 20, and 50 in Li||NMC811 cells with 50-pm Li anode and high-loading NMC811 cathode using 1.2 M LiFSI in F5DEE and 2 M LiFSI in F3EME with 1 wt.% LiDFP additive. Cells were cycled between 2.8 V and 4.4 V at 2 mA cm’2charge current density and 4 mA- cm’2discharge current density.

[0043] FIG. 28 shows discharge capacity of Li||LFP coin cells with 20-pm thick Li anode and high-loading LFP cathode using 1.2 M LiFSI in F5DEE, and 2 M LiFSI in F2DEM, EME, F1EME, F2EME, and F3EME. Cells were cycled between 2.5 V and 3.8 V at 1.5 mA cm’2charge and 3 mA- cm’2discharge current density.64902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0044] FIG. 29 shows discharge capacity and CE of anode-free LFP pouch cells using 2 M LiFSI in EME, F2EME, and F3EME under C / 2 charge and C / 2 discharge. Replicated cells are shown.

[0045] FIG.30 shows discharge capacity and CE of anode-free LFP pouch cells using 2 M LiFSI in F2EME and F3EME under C / 2 charge and 2C discharge. Replicated cells are shown.

[0046] FIG.31 shows discharge capacity and CE of anode-free NMC532 (left) and Ni95 (right) pouch cells using 2 M LiFSI in F3EME under C / 2 charge and 1C discharge. Replicated cells are shown.

[0047] FIG.32 shows discharge capacity of Li||SPAN coin cells with 100-pm thick Li anode and high-loading SPAN (6.5 mAh cm'2) using 2 M LiFSI in EME, F1EME, F2EME, and F3EME. The cells were cycled between 1.0 V and 3.0 V with 0.2 C discharge and charge current density. Replicated cells are shown.

[0048] FIG.33 shows discharge capacity of Li||2 mAh cm'2Si using LP40, and 2 M LiFSI in EME, F2EME, and F3EME. Cells were cycled between 0 V and 1.0 V with various charge and discharge current densities (0.125 mA cm'2, 0.25 mA cm'2, 0.5 mA cm'2, and 0.75 mA cm'2).DETAILED DESCRIPTION

[0049] The present embodiments will now be described in detail with reference to the drawings, which are provided as illustrative examples of the embodiments so as to enable those skilled in the art to practice the embodiments and alternatives apparent to those skilled in the art. Notably, the figures and examples below are not meant to limit the scope of the present embodiments to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present embodiments can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present embodiments will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the present embodiments.74902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0050] In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the present disclosure is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present embodiments encompass present and future known equivalents to the known components referred to herein by way of illustration.Electrolyte Compositions

[0051] In one aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to an electrolyte composition for a lithium-metal battery, the electrolyte composition comprising:a lithium compound; anda solvent selected from:an asymmetric non-fluorinated ether selected from 1,2-methoxy ethoxy ethane (EME), 1 -methoxy -2-propoxy ethane (MPE), l-methoxy-2-isopropoxy ethane (MiPE), and combinations thereof;a fluorinated asymmetric ether;a fluorinated asymmetric acetal; andcombinations thereof.Solvent

[0052] In electrolyte compositions according to the present disclosure, the solvent may comprise an asymmetric non-fluorinated ether, a fluorinated asymmetric ether, an asymmetric acetal, or a a fluorinated asymmetric acetal. The solvent may be any one or more representatives of the above genera of compounds sufficient to ensure high conductivity, oxidative stability, thermal stability, ready dissociation into free Li+ions and anions, coulombic efficiency, and good SEI-forming ability. In some embodiments, the solvent comprises an ethylene glycol backbone (O-C-C-O) due to its chelation capability and high ionic conductivity.84902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0053] In some embodiments, the solvent comprises asymmetric non-fluorinated ethers. As used herein, the term “asymmetric ether” means an ether in which the two carbon-containing groups (alkyl, aryl, or other organic substituents) bonded to the central oxygen atom are different from one another — that is, the ether has the general structure R-O-R' where R and R' are dissimilar organic groups. Because the substituents differ, the molecule lacks the internal symmetry found in a “symmetric” (or “simple”) ether where R and R' are identical.

[0054] In some embodiments, the asymmetric, non-fluorinated ether comprises, but is not limited to, 1,2-methoxy ethoxy ethane (“EME”), l-methoxy-2-propoxy methane (“MPM”), 1-methoxy-2-propoxy ethane (“MPE”), 1 -methoxy -2-isopropoxy ethane (“MiPE”), and combinations thereof. (See, e.g., FIG. 7.) In some embodiment, the solvent comprises EME.

[0055] In some embodiments, the solvent comprises one or more asymmetric fluorinated ethers. As used herein, the term “asymmetric fluorinated ether” means an asymmetric ether in which at least one fluorine atom is bonded to a carbon atom. That is, an “asymmetric fluorinated ether” may be a fluorinated derivative of an asymmetric non-fluorinated ether, wherein one or more of the carbon-bonded hydrogen atoms in the asymmetric non-fluorinated ether has been replaced by a fluorine atom. In some embodiments, the asymmetric fluorinated ether has a fluorination degree x, wherein x is the number of fluorine atoms present in a molecule of the asymmetric fluorinated ether. In some embodiments, x is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, x is 1, 2, 3, or 4. In some embodiments, x is 1, 2, or 3. In some embodiments, x is 2 or 3. In some embodiments, x is 1. In some embodiments, x is 2. In some embodiments, x is 3.

[0056] In some embodiments, the asymmetric fluorinated ether comprises, but is not limited to, fluorinated derivatives of 1,2-methoxy ethoxy ethane (“EME”), fluorinated derivatives of 1-methoxy-2-propoxy ethane (“MPE”), fluorinated derivatives of l-methoxy-2-isopropoxy ethane (“MiPE”), and combinations thereof. In some embodiments, the solvent comprises F1EME, F2EME, F3EME, or any combination thereof. (See, e.g., FIGs. 1-6.) In some embodiments, the solvent comprises F2EME. In some embodiments, the solvent comprises F3EME.

[0057] In some embodiments, the solvent comprises an asymmetric acetal. As used herein, the term “asymmetric acetal” means an acetal in which the two organic groups (designated R and R')94902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTattached to the central carbon atom through separate -OR and -OR' linkages (or - OR' and -OR", depending on notation) are different from one another. In structural terms, an asymmetric acetal has the general form R-CH(OR')(OR") where R' and R" (or R and R', depending on notation) are dissimilar alkyl, aryl, or other organic substituents. Because these substituents are not identical, the molecule lacks the internal symmetry present in a symmetric (or “simple”) acetal where the two -OR groups are the same.

[0058] In some embodiments, the solvent comprises a fluorinated asymmetric acetal. As used herein, the term “asymmetric fluorinated acetal” means an asymmetric acetal in which at least one fluorine atom is bonded to a carbon atom. That is, an “asymmetric fluorinated acetal” may be a fluorinated derivative of an asymmetric non-fluorinated acetal, wherein one or more of the carbon-bonded hydrogen atoms in the asymmetric non-fluorinated acetal has been replaced by a fluorine atom. In some embodiments, the asymmetric fluorinated acetal has a fluorination degree x, wherein x is the number of fluorine atoms present in a molecule of the asymmetric fluorinated acetal. In some embodiments, x is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, x is 1, 2, 3, or 4. In some embodiments, x is 1, 2, or 3. In some embodiments, x is 2 or 3. In some embodiments, x is 1. In some embodiments, x is 2. In some embodiments, x is 3.

[0059] Scheme 1 below shows some non-limiting examples of asymmetric ether molecules or acetal molecules and their fluorinated derivatives. (Left column: asymmetric acetal and its fluorinated derivative; middle left: 1 -methoxy-2-propoxy methane (MPM), middle right: fluorinated MPE, right: fluorinated MiPE)104902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTScheme 1. Exemplary Solvent MoleculesLithium Compounds

[0060] The electrolyte composition may comprise any suitable lithium compound to ensure high conductivity, oxidative stability, thermal stability, ready dissociation into free Li+ions and anions, and good SEI-forming ability. In some embodiments, the lithium compound comprises lithium bis(fluorosulfonyl)imide (“LiFSI”), lithium bis(trifluoromethanesulfonyl)imide (“LiTFSI”), lithium bis(pentafluoroethanesulfonyl)imide (“LiBETI”), lithium (trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide (LiCSA), LiB(CF3SO2)4, LiN(SC>2C2F5)2, LiPFe, LiCIC , LiBF4, LiAsFe, or any combination thereof. In some embodiments, the lithium compound comprises LiFSI.

[0061] The lithium compound may be present in the electrolyte composition at any suitable concentration to ensure high conductivity, oxidative stability, thermal stability, and good SEI-forming ability. In some embodiments, the lithium compound is present in the electrolyte composition at a concentration of at least about 0.1 M, at least about 0.2 M, at least about 0.3 M, at least about 0.4 M, at least about 0.5 M, at least about 0.6 M, at least about 0.7 M, at least about 0.8 M, at least about 0.9 M, at least about 1.0 M, at least about 1.1 M, at least about 1.2 M, at 114902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTleast about 1.3 M, at least about 1.4 M, at least about 1.5 M, at least about 1.6 M, at least about 1.7 M, at least about 1.8 M, at least about 1.9 M, at least about 2.0 M, at least about 2.1 M, at least about 2.2 M, at least about 2.3 M, at least about 2.4 M, at least about 2.5 M, at least about 3.0 M, at least about 3.5 M, at least about 4.0 M, at least about 4.5 M, at least about 5.0 M, at least about 5.5 M, at least about 6.0 M, at least about 6.5 M, at least about 7.0 M, at least about 7.5 M, at least about 8.0 M, at least about 8.5 M, at least about 9.0 M, at least about 9.5 M, at least about 10.0 M, or any range or value including and / or in between any two of these values.

[0062] In some embodiments, the lithium compound is present in the electrolyte composition at a concentration of less than or equal to about 10.0 M, less than or equal to about 9.5 M, less than or equal to about 9.0 M, less than or equal to about 8.5 M, less than or equal to about 8.0 M, less than or equal to about 7.5 M, less than or equal to about 7.0 M, less than or equal to about 6.5 M, less than or equal to about 6.0 M, less than or equal to about 5.5 M, less than or equal to about 5.0 M, less than or equal to about 4.5 M, less than or equal to about 4.0 M, less than or equal to about 3.5 M, less than or equal to about 3.0 M, less than or equal to about 2.5 M, less than or equal to about 2.4 M, less than or equal to about 2.3 M, less than or equal to about 2.2 M, less than or equal to about 2.1 M, less than or equal to about 2.0 M, less than or equal to about 1.9 M, less than or equal to about 1.8 M, less than or equal to about 1.7 M, less than or equal to about 1.6 M, less than or equal to about 1.5 M, less than or equal to about 1.4 M, less than or equal to about 1.3 M, less than or equal to about 1.2 M, less than or equal to about 1.1 M, less than or equal to about 1.0 M, less than or equal to about 0.9 M, less than or equal to about 0.8 M, less than or equal to about 0.7 M, less than or equal to about 0.6 M, less than or equal to about 0.5 M, less than or equal to about 0.4 M, less than or equal to about 0.3 M, less than or equal to about 0.2 M, less than or equal to about 0.1 M, or any range or value including and / or in between any two of these values.

[0063] In some embodiments, the lithium compound is present in the electrolyte composition at a concentration of about 0.1 M to about 10 M, about 0.5 M to about 5 M, about 1 M to about 5 M, about 1.0 M to about 4.0 M, about 1.0 M to about 3.5 M, about 1.0 M to about 3.0 M, about 1.0 M to about 2.5 M, about 1.0 M to about 2.0 M, about 1.5 M to about 5.0 M, about 1.5 M to124902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTabout 4.0 M, about 1.5 M to about 3.5 M, about 1.5 M to about 3.0 M, about 1.5 M to about 2.5 M, or any range or value therein.Additives

[0064] The electrolyte composition according to the present disclosure may further comprise one or more electrolyte additives. The electrolyte additive may be any suitable compound for forming a stable solid-electrolyte interphase (“SEI”), suppressing dendrite growth, regulating Li deposition, extending oxidative or reductive stability windows, scavenging water, HF, or other species, improving low-temperature battery performance, or reducing flammability. In some embodiments, the electrolyte additive comprises fluor oethylene carbonate (FEC), vinylene carbonate (VC), lithium nitrate (LiNC ), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), l,3,2-dioxathiolane-2,2-dioxide (DTD), tris(trimethylsilyl) phosphite (TMSPi) or related trialkyl / aryl phosphites, tri s(trimethyl silyl) phosphate (TMSP) and other flame-retardant phosphates / phosphonates, alkali-metal fluorides (e.g., cesium fluoride) (for dendrite suppression), iodide salts (e.g, Lil) (for surface redox and SEI modification), lithium difluorophosphate (LiDFP), or any combination thereof. In some embodiments, the electrolyte additive comprises LiDFP.

[0065] The electrolyte additive may be present at any suitable concentration for forming a stable solid-electrolyte interphase (“SEI”), suppressing dendrite growth, regulating Li deposition, extending oxidative or reductive stability windows, scavenging water, HF, or other species, improving low-temperature battery performance, or reducing flammability. In some embodiments, the electrolyte additive is present in the electrolyte composition at a concentration, relative to the total weight of the electrolyte composition, of at least about 0.1 wt.%, at least about 0.2 wt.%, at least about 0.3 wt.%, at least about 0.4 wt.%, at least about 0.5 wt.%, at least about 0.6 wt.%, at least about 0.7 wt.%, at least about 0.8 wt.%, at least about 0.9 wt.%, at least about 1 wt.%, at least about 1.5 wt.%, at least about 2 wt.%, at least about 2.5 wt.%, at least about 3 wt.%, at least about 3.5 wt.%, at least about 4 wt.%, at least about 4.5 wt.%, at least about 5 wt.% , or any range or value including and / or in between any two of these values.134902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0066] In some embodiments, the electrolyte additive is present in the electrolyte composition at a concentration, relative to the total weight of the electrolyte composition, of less than or equal to about 5 wt.%, less than or equal to about 4.5 wt.%, less than or equal to about 4 wt.%, less than or equal to about 3.5 wt.%, less than or equal to about 3 wt.%, less than or equal to about 2.5 wt.%, less than or equal to about 2 wt.%, less than or equal to about 1.5 wt.%, less than or equal to about 1 wt.%, less than or equal to about 0.9 wt.%, less than or equal to about 0.8 wt.%, less than or equal to about 0.7 wt.%, less than or equal to about 0.6 wt.%, less than or equal to about 0.5 wt.%, less than or equal to about 0.4 wt.%, less than or equal to about 0.3 wt.%, less than or equal to about 0.2 wt.%, less than or equal to about 0.1 wt.%, or any range or value including and / or in between any two of these values.

[0067] In some embodiments, the electrolyte additive is present in the electrolyte composition at a concentration, relative to the total weight of the electrolyte composition, of about 0.1 wt.% to about 5 wt.%, about 0.5 wt.% to about 5 wt.%, about 1 wt.% to about 5 wt.%, about 1.5 wt.% to about 5 wt.%, about 2 wt.% to about 5 wt.%, about 2.5 wt.% to about 5 wt.%, about 0.5 wt.% to about 1 wt.%, about 0.5 wt.% to about 1.5 wt.%, about 0.5 wt.% to about 2 wt.%, about 0.5 wt.% to about 2.5 wt.%, about 0.5 wt.% to about 3 wt.%, about 0.5 wt.% to about 4 wt.%, about 0.1 wt.% to about 1 wt.%, about 0.1 wt.% to about 1.5 wt.%, about 0.1 wt.% to about 2 wt.%, about 0.1 wt.% to about 2.5 wt.%, about 0.1 wt.% to about 3 wt.%, about 0.1 wt.% to about 4 wt.%, about 0.5 wt.% to about 1.5 wt.%, or any range or value therein.Li Metal Batteries

[0068] In another aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to a battery, comprising:a cathode current collector:a cathode in contact with the current collector;an anode opposite the cathode, wherein the anode comprises lithium metal;an anode current collector in contact with the anode; andthe electrolyte composition according to any of the embodiments disclosed herein between the anode and the cathode.144902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT

[0069] In some embodiments, the battery is a lithium metal battery.

[0070] The cathode may be any suitable material to provide a balance of energy density, rate capability, cycle life, and thermal stability. In some embodiments, the cathode comprises a layered oxide selected from lithium cobalt oxide (LiCoCh), lithium nickel manganese cobalt oxide (LiNi.vMnjCozO , NMC), or lithium nickel cobalt aluminum oxide (LiNixCo AlzCh, NCA). In some embodiments, the cathode comprises a spinel oxide such as lithium manganese oxide (LiMn2O4) or a high-voltage spinel such as lithium manganese nickel oxide (LiMm.5Nio.5O4). In some embodiments, the cathode comprises a polyanion compound, such as lithium iron phosphate (LiFePO4, LFP). In some embodiments, the cathode comprises a lithium-rich layered oxide, a mixed-metal oxide, or combinations thereof.

[0071] The anode may comprise any suitable material to provide a balance of high capacity, low electrochemical potential, cycling stability, and safety. In some embodiments, the anode comprises metallic lithium, such as lithium foil, lithium powder, or lithium deposited in situ during cell operation. In some embodiments, the anode comprises a lithium alloy (e.g., an alloy of lithium with aluminum, silicon, tin, or magnesium). In some embodiments, the anode comprises a composite structure comprising lithium metal in combination with a carbon host, a polymer matrix, or a ceramic framework configured to improve mechanical stability and suppress dendrite formation. In some embodiments, the anode comprises a lithium-coated current collector, such as a copper foil or other conductive substrate.

[0072] In some embodiments, the anode may also comprise a next-generation lithium metal structure designed to address dendrite growth, safety, and cycle-life limitations of conventional metallic lithium anodes. In some embodiments, the anode comprises a three-dimensional (3D) porous metallic scaffold, such as a copper, nickel, or carbon foam, into which lithium is deposited. In some embodiments, the anode comprises a lithium-sulfur host system, wherein the lithium metal anode is paired with sulfur or sulfur-polymer cathodes and protected by interlayers, artificial solid-electrolyte interfaces, or functional coatings. In some embodiments, the anode comprises a protected lithium metal electrode, such as a lithium surface coated with a polymer electrolyte, ceramic electrolyte, or hybrid artificial solid-electrolyte interface. In some154902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTembodiments, the anode comprises a lithium-carbon or lithium-silicon composite host designed to buffer volume changes and stabilize cycling. In some embodiments, the anode comprises lithium metal combined with solid-state electrolytes, including sulfides, oxides, or garnet-type ceramics.

[0073] The cathode current collector and / or anode current collector, may comprise copper, aluminum, nickel, stainless steel, titanium, a carbon-based substrate, or any combination thereof.

[0074] In some embodiments according to the present disclosure, the battery further comprises a separator. The separator may comprise any suitable material to provide ionic conductivity while electronically insulating the anode and cathode. In some embodiments, the separator comprises microporous polyolefins such as polyethylene (PE) and polypropylene (PP), multilayer PE / PP composites, ceramic-coated polyolefins, and nonwoven polymer membranes. In some embodiments, the separator comprises inorganic solid electrolytes, such as sulfide-based, oxidebased, or garnet-type ceramics, polymer-ceramic composites, or any combination thereof. In some embodiments, the separator comprises a CELGARD™™ microporous polyolefin membrane.Methods of Making Batteries

[0075] In another aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to a method of making a battery, the method comprising:combining a lithium compound and a solvent to produce the electrolyte composition according to any of the embodiments disclosed herein;contacting a cathode with a cathode current collector;contacting an anode comprising Li metal with an anode current collector, the anode being opposite the cathode; anddisposing the electrolyte composition between the cathode and the anode to obtain the battery.

[0076] In some embodiments, any of the above steps are performed in inert atmosphere. In some embodiments, the method further comprises disposing a separator between the anode and the164902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTcathode. In some embodiments, the method further comprises enclosing the battery in a casing (or “housing”).EXAMPLES

[0077] Reference will now be made in detail to some specific embodiments contemplated by the present disclosure. While various embodiments are described herein, it will be understood that it is not intended to limit the present technology to the described embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the technology as defined by the appended claims.Example 1. Synthesis of F1EME, F2EME, F3EME

[0078] Materials. 2-methoxy ethanol was purchased from Sigma-Aldrich. 2,2,2-trifluoroethyl p-toluenesulfonate and 2,2-difluoroethanol were purchased from SynquestLab. 2-fluoroethanol was purchased from Matrix Scientific. Ethylene carbonate, p-toluenesulfonyl chloride, sodium hydride (60% in mineral oil), methyl iodide, tetraglyme, triethylamine and other general reagents were purchased from Sigma-Aldrich, Fisher Scientific, or TCI.

[0079] Referring to FIG. 1, to synthesize F1EME, 2-fluoroethyl tosylate was first synthesized (e.g, as described in 12 J. Mater. Chem. A, 2986-2993 (2024)). To a 500-mL round flask in ice bath was added 19.2 g (0.300 mol) of 2-fluoroethanol, 60.05 g (0.315 mol) of p-toluenesulfonyl chloride, 45.9 mL (0.33 mol) of triethylamine, and 200 mL of DCM. The suspension was stirred for one day at room temperature, after which the DCM phase was washed with 300 mL aqueous NaHCCh solution, 2 x 300 mL DI water, and then 300 mL brine. The DCM phase was then collected and dried with anhydrous NaSCh. After filtration, DCM was removed by rotary evaporation, and the product was obtained as a pale orange liquid.

[0080] F1EME was synthesized through reaction between 2-methoxy ethanol and the obtained 2-fluoroethyl tosylate. 7.05 g (92.7 mmol) of 2-methoxy ethanol was dissolved in 200 mL dry THF, and the solution was cooled with an ice bath. NaH (4.67 g, 60%, 116 mmol) was added and stirred for 2 h, after which 2-fluroethyl tosylate (21.12 g, 97.3 mmol) was added. The resulting mixture was further stirred for 2 h and then refluxed overnight at 60 °C. The suspension was 174902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTfiltered and rinsed with THF after cooling to room temperature. Then, the filtered solution underwent vacuum distillation (vapor temperature ~70-75°C at ~90 mbar) four times to obtain a colorless and pure F1EME. Yield: ~ 40%. FIG.2 showsJH (top),13C (middle), and19F (bottom) NMR spectra of F1EME in CDCh.

[0081] Referring to FIG.3, to synthesize F2EME, 2-(2,2-difluoroethoxy) ethanol was first prepared (e.g., as described in 7 Nature Energy 94-106 (2022)). To a 500-mL round flask was added 75 g (0.914 mol) of 2,2-difluoroethanol, 70 g (0.795 mol) of ethylene carbonate, 4 g of NaOH, and 100 mL of tetraglyme. The suspension was heated to 140 °C and stirred for 72 h. The resulting black-colored suspension was then distilled under vacuum three times to obtain a colorless liquid as a product.

[0082] F2EME was synthesized through methoxylation of the obtained product. To a 1-L round flask was added 30 g (0.238 mol) of 2-(2,2-difluoroethoxy) ethanol, 67.6 g (0.476 mol) of Mel, 63.4 g (1.189 mol) of NaOH, and 400 mL of THF. The suspension was stirred at room temperature for 2 h, and the flask was heated to 60°C to reflux for 2 days. The suspension was filtered, and the remaining THF in the resulting solution was removed via rotary evaporation. The product underwent vacuum distillation (vapor temperature ~70-75°C at ~90 mbar) four times, to obtain a colorless liquid as the product. Yield: ~ 80 %. FIG. 4 shows 'H (top),13C (middle), and19F (bottom) NMR spectra of F2EME in CDCh.

[0083] Referring to FIG. 5, to synthesize F3EME, to a 500-mL round flask was added 22.8 g (0.300 mol) of 2-methoxy ethanol, which was dissolved with 200 mL dry THF, after which the solution was cooled with an ice bath. NaH (14.4 g, 60%, 0.360 mmol) was added and stirred for 2 h, after which 2,2,2-trifluoroethyl p-toluenesulfonate (80.0 g, 0.315 mol) was added. The resulting mixture was further stirred for 2 h and then refluxed overnight at 60°C. The suspension was filtered and rinsed with THF after cooling to room temperature. Then, the filtered solution underwent vacuum distillation (vapor temperature ~ 45-50°C at 90 mbar) four times, to obtain a colorless liquid as the product. Yield: ~ 55%. FIG. 6 shows 'H (top),13C (middle), and19F (bottom) NMR spectra of F3EME in CDCh.184902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTExample 2. Comparison of Asymmetric Solvents (EME, MPE, MiPE) to Symmetric Solvents (DME, DEE)

[0084] To systematically study a set of asymmetric solvents versus a set of symmetric solvents, electrolyte properties and lithium metal coulombic efficiency (CE) were measured in five total electrolyte compositions (1 M LiFSI in EME, MPE, MiPE, DME, and DEE). EME, MPE, and MiPE were synthesized as shown in FIG. 7. ResultingNMR spectra of EME, MPE, and MiPE are shown in FIG. 8, FIG. 9, and FIG. 10, respectively.Solvation Strength A Ionic Conductivity

[0085] Solvation strength of each electrolyte was measured quantitatively with a solvation free energy measurement and qualitatively with Raman spectroscopy. Relative solvation free energy (AGsoiv) is measured according to the method described in Kim. et al., 143 J. Am. Chem. Soc. 10301-10308 (2021). A higher value of AGsoiv implies weaker coordination of solvent with Li+, and therefore more FST anion in the inner solvation shell. Referring to FIG. 11, AGsoiv increases in the order of DME < EME < MPE~MiPE~DEE, resulting in weaker solvation for MPE, MiPE, and DEE. The data indicates that a larger carbon chain leads to increased steric hindrance, which is consistent with the trend of AGsoiv in these electrolytes. Raman spectroscopy was also performed. Raman shifts at 710 cm-1and 721 cm'1are referred to as the free FST and contact-ion pair (CIP), respectively. 1 M LiFSI in EME, MPE, MiPE, and DEE shows a very similar spectrum, showing larger amounts of CIP than 1 M LiFSI in DME. Thus, both solvation free energy measurements and Raman spectroscopy confirm that EME-, MPE-, MiPE-, and DEE-based electrolytes have weaker solvation strength than DME.

[0086] Referring to FIG. 12, ionic conductivity of 1 M LiFSI in each solvent was measured in a coin cell with 25 pm PE separator. As shown in the data, ionic conductivity increases in the order of DEE~MiPE~MPE < EME < DME.194902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTCoulombic Efficiency

[0087] Referring now to FIG. 13, Li metal coulombic efficiency (CE) of each electrolyte was measured in a Li||Cu coin cell with 25 pm PE separator. Li plating and stripping with current density of 0.5 mA and cut-off capacity of 1 mAh was chosen as a standard CE test. CE tests with two replicative coin cells for each electrolyte composition are also shown in FIG. 14. Symmetric solvent (DME, DEE) based electrolytes have large fluctuation in CE (see FIG. 14, panel (a)), while asymmetric solvent (EME, MPE, MiPE) based electrolytes show stable CE near 99.0% (see FIG. 14, panel (b)). Among the asymmetric solvents, EME has slightly higher CE than MPE or MiPE.

[0088] 1 M LiFSI in DEE is known to have stable CE in Li||Cu (using CELGARD™ 2325 separator) according to Chen, et al., 143 J. Am. Chem. Soc. 18703-18713 (2021). However, in the present study, CE results using a PE separator with the same thickness as the CELGARD™ 2325 separator in Chen et al. were different, perhaps due to the differences in mechanical properties between the PE and CELGARD™ 2325 separators.Example 3. Comparison Among DME-, EME-, and DEE-based Electrolytes

[0089] Referring to FIG. 15, DME-, EME-, and DEE-based electrolytes were compared using CELGARD™ 2325 separator. DME is commonly known to have strong solvation power due to its chelating capability. Recently, DEE, with increased steric hindrance of terminal alkyl groups, has been shown to have weaker solvation ability, which results in favorable anion-derived SEI and higher lithium metal compatibility. Herein, asymmetric EME solvent has been shown to preserve the steric hindrance effect observed for DEE while also enhancing ionic conductivity in a manner similar to DEE, which might be useful in high-rate conditions.

[0090] Referring to FIG. 16, 1 M LiFSI in DME, EME, and DEE electrolytes were tested in Li||Cu coin cells to observe the coulombic efficiency of lithium plating and stripping. Different current densities (0.2, 0.5, and 2 mA) with the same cut-off capacity (1 mAh) were applied to observe the rate-performance of each electrolyte. 1 M LiFSI in DME appeared to have a large204902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTfluctuation in CE for overall current density, while EME- and DEE-based electrolytes showed a stable and high CE, but with different performance at different current densities.

[0091] Referring now to FIG. 17, in low current density (0.2 mA), the CEs of EME- and DEE-based electrolytes were similar, but as current density become higher, the difference in CE between 1 M LiFSI in EME and DEE appears to increase.Example 4. EME Solvent for Localized High-concentration Electrolyte (LHCE)

[0092] Localized high-concentration electrolyte (LHCE) represent one strategy to enhance the performance of lithium -metal batteries. For proof-of-concept, LHCEs with different solvents (DME, EME, and DEE) were obtained by mixing LiFSI, solvent, and TTE in same molar ratio (LiFSEsolvent / TTE = 1 / 1.2 / 3 (m / m / m)), then testing CE. As shown in FIG. 18, all LHCEs show similar performance in Li||Cu long cycling CE tests. EME-based LHCE shows slightly higher CE (98.74 %) than DME-based LHCE (98.62%) and DEE-based LHCE (98.66 %).Example 4. Fluorinated EME Solvents for High-voltage Lithium Metal Batteries

[0093] Among the asymmetric electrolytes tested in Examples 2-4, the EME-based electrolyte showed not only the highest coulombic efficiency but also the highest ionic conductivity. To test the effect of fluorination on asymmetric solvent performance, fluorination on the beta carbon of EME was performed to different degrees. (See Example 1, FIGs. 1-6.) Comparison among EME and fluorinated EMEs (l-methoxy-2-(2-fluoroethoxy)ethane (F1EME), l-methoxy-2-(2,2-difluoroethoxy)ethane (F2EME), and l-methoxy-2-(2,2,2-trifluoroethoxy) ethane (F3EME)) is discussed below.Ionic Conductivity

[0094] Ionic conductivities of x M LiFSI in EME, Fl EME, F2EME, F3EME (x = 1, 2, 3, 4) was measured in coin cells with CELGARD™ 2325 separator to optimize the concentration for higher ionic conductivities. As shown in FIG. 19, 2 M was the concentration showing the highest ionic conductivity overall. Further, as the degree of fluorination increased, conductivity was observed to decrease. However, 2 M LiFSI in F3EME, which showed the lowest ionic214902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTconductivity among these electrolytes, still has a higher ionic conductivity value than the state-of-the-art solvent-based electrolytes, 1.2 M LiFSI in F5DEE (reported in WIPO Publication No.2023 / 215607A1) and 2 M LiFSI in F1DEM (reported in WIPO Publication No.2023 / 215607A1).Solvation Strength

[0095] Referring to FIG. 20, solvation strengths for each electrolyte were measured in the same way for comparing non-fluorinated ether solvents, described in Example 2 above. AGsoiv increases as the degree of fluorination becomes higher, indicating increased fluorination results in weaker solvation. Raman spectroscopy also confirmed that higher degree of fluorination leads to weaker coordination with Li-. The Ramans shifts at 710 cm1, 721 cm1, and 736 cm1are referred to as free FSF (solvent separated ion pair, SSIP), contact-ion pair (CIP), and aggregates (AGG), respectively. 2 M LiFSI in EME and F1EME show very similar spectra with similar peaks for SSIP. As the degree of fluorination increases from one to two to three, the percentage of CIP and AGG increases, which is well aligned with the solvation free energy results.Li Metal Coulombic Efficiency

[0096] The average CE of each electrolyte was evaluated by the Aurbach method in Li-Cu half cells. Based on this standard protocol, 5 mAh cm'2of Li is first deposited onto the Cu foil as a Li reservoir, followed by 10 subsequent cycles of plating and stripping at 0.5 mA- cm'2for 1 mAh- cm'2. Finally, all deposited Li is stripped from Cu, and the total capacity recovered is divided by the amount deposited to obtain the CE. The average CE of three cells calculated based on this method is shown in FIG.21. 2 M LiFSI in F3EME gave the highest CE of 99.5 %, which is comparable to the 99.5 % CE previously observed with F5DEE (reported in WIPO Publication No. 2023 / 215607A1) and F1DEM (reported in WIPO Publication No.2023 / 215607A1).

[0097] Li||Cu long cycling coulombic efficiency (CE) of each electrolyte was also measured. Li plating and stripping with current density of 0.5 mA and cut-off capacity of 1 mAh was chosen as a standard CE test. FIG. 22 shows the results of these tests, using two replicative coin cells for224902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTeach electrolyte composition. Average CE descends in the following order: F3EME > F2EME ~ EME > F1EME. Notably, for 2 M LiFSI in F3EME, the average CE (40-100 cycles) was 99.3%, and the number of activation cycles to reach 99.0% was only 3 cycles.Overpotential

[0098] Overpotential was measured in Li||Li symmetric cells for each electrolyte. In FIG. 23, panel (a) shows the voltage profde of Li||Li cell with a current density of 1 mA cm'2and capacity of 1 mAh cm'2, and panel (b) shows the zoomed-in voltage profile. Overpotential increased in the following order: EME < F1EME < F2EME < F3EME, which is well aligned with the previous ionic conductivity results (see FIG. 19). To assess the fast-charging capability, Li||Li cycling with a different current density from 1 mA- cm'2to 10 mA- cm'2(10 cycles at each) and a capacity of 3 mAh- cm'2was also performed (FIG. 23, panel (c)). All electrolytes show a stable voltage profile in 10 mA cm'2condition, compared to the previously reported F5DEE (reported in WIPO Publication No. 2023 / 215607A1) and F1DEM (reported in WIPO Publication No. 2023 / 215607A1)..Oxidation Stability

[0099] Linear sweep voltammetry (LSV) was performed in Li| | Al and Li||Pt cells with each electrolyte to test the oxidation stability. The voltage was slowly increased from an open circuit to 4.4 V at a scan rate of 1 mV- s'1. As shown in FIG.24, oxidation stability improves as the degree of fluorination on the solvent becomes higher. LSV tests on Li||Pt were also performed to observe the intrinsic oxidation stability of each electrolyte. EME- and FlEME-based electrolytes already showed an increase in leakage current after 2.0 V, while F2EME- and F3EME-based electrolytes had an increased oxidation stability. However, 2 M LiFSI in F2EME showed two distinct peaks around 3.1 V and 3.5 V, which may indicate decomposition of electrolytes.234902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTLi\ \NMC811 Coin Cell Performance

[0100] Cycling performance of each electrolyte was evaluated in 50-pm Li||4.9 mAh cm'2NMC811 coin cell. Current density of 0.8 mA cm’2charge and 1.3 mA cm’2discharge was applied. As shown in FIG. 25, the cyclability decreased in the following order: 2 M LiFSI in F3EME > EME > F2EME > F1EME. The cycle number at which 80 % retention was obtained was >160 cycles for 2 M LiFSI in F3EME, indicating that F3EME is an excellent candidate for high-voltage lithium-metal batteries.

[0101] To fully understand the advantages of high ionic conductivity of fluorinated EME-based electrolytes, high-rate condition of 2 mA cm’2charge and 4 m- cm’2discharge was applied. As shown in FIG. 26, with 1.2 M LiFSI in F5DEE — which could not be cycled over 50 cycles (80% capacity retention) — 2 M LiFSI in F3EME outperformed in high-rate condition, cycling over 100 cycles to 80% capacity retention. To improve the oxidation stability, 2 M LiFSI in F3EME with 1 wt.% of LiDFP was also prepared and cycled, showing enhanced cyclability and more stable CE.

[0102] Capacity -voltage profiles for high-rate cycling of Li||NMC811 (using 1.2 M LiFSI in F5DEE and 2 M LiFSI in F3EME with 1 wt.% LiDFP) are shown in FIG. 27. While 1.2 M LiFSI in F5DEE shows large overpotential and sudden decrease in capacity after 50 cycles, F3EME-based electrolyte cycles more stably in high-rate conditions.Li\ \LFP Coin Cell Performance

[0103] Cycling performance of each electrolyte was evaluated in 20-pm Li||3 mAh cm’2NMC811 coin cell. High current density of 1.5 mA cm’2charge and 3 mA cm’2discharge was applied. As shown in FIG. 28, except for F1EME -based electrolyte, EME-, F2EME-, and F3EME-based electrolyte outperformed previously reported F IDEM or F5DEE-based electrolytes, cycling over 250 cycles. 2 M LiFSI in F3EME showed the best performance among the electrolytes, cycling nearly 350 cycles (80% capacity retention). The data demonstrates the excellent and unexpected rate performance of EME and fluorinated EME electrolytes, when compared to previous state-of-the-art electrolytes.244902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTCM | LFP Anode-free Pouch Cell Performance

[0104] The performance of each electrolyte was further assessed in anode-free pouch cells, with a voltage range of 2.5 V to 3.65 V. As shown in FIG. 29, 2 M LiFSI in EME, F2EME, and F3EME were compared under 0.5 C charging and 0.5 C discharging rate (1C = 200 mA). Cyclability was higher in the order of F3EME > F2EME > EME. Higher-rate (0.5 C charge, 2 C discharge) was applied for 2 M LiFSI in F2EME and F3EME, since slow charge and fast discharge conditions generally improved the lithium morphology (see FIG. 30). Both F2EME and F3EME showed stable cycling and CE over 80 cycles.Cu\ NMC532, Ni95 Anode-free Pouch Cell Performance

[0105] Anode-free Cu||NMC532 and Ni95 pouch cells were cycled using 2 M LiFSI in F3EME electrolyte under high-rate current density (0.5 C charge, 1 C discharge, 1C = 200 mA) and voltage range of 3.0 V to 4.2 V. As shown in FIG.31, both cathodes can be cycled in F3EME-based electrolyte for over 50 cycles.Li\ \SPAN Coin Cell Performance

[0106] 100-pm Li||6.5 mAh cm’2sulfurized polyacrylonitrile (SPAN) electrode full cells were also cycled with each electrolyte under 0.2 C charge and 0.2 C discharge current density and a voltage range of 1.0 V to 3.0 V. As shown in FIG. 32, FlEME-based electrolytes show low cyclability in SPAN full cells, F2EME and F3EME-based electrolytes in SPAN full cells were cycled over 50 cycles. F3EME also shows surprisingly higher capacity utilization when compared to the other electrolytes tested.Li\ \Si Coin Cell Performance

[0107] Referring to FIG.33, 2 M LiFSI in EME, F2EME, and F3EME electrolyte were also cycled with Si anodes under different c-rates from 0.125 mA to 0.75 mA. LP40 was also cycled for comparison. Capacity utilization descended in the following order: F3EME > F2EME > EME > LP40 throughout all current densities, again showing the surprisingly high capacity254902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTutilization achieved by F3EME-, F2EME-, and EME-based electrolytes. The capacity utilization for F3EME-based electrolyte compositions, in particular, was surprisingly high.

[0108] The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are illustrative, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably coupleable," to each other to achieve the desired functionality. Specific examples of operably coupleable include but are not limited to physically mateable and / or physically interacting components and / or wirelessly interactable and / or wirelessly interacting components and / or logically interacting and / or logically interactable components.

[0109] With respect to the use of plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for sake of clarity.

[0110] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc ).

[0111] Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified264902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTdifferently above. Also, two or more steps may be performed concurrently or with partial concurrence, unless specified differently above. Such variation may depend, for example, on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations of the described methods could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps.

[0112] It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and / or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).

[0113] Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general, such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to274902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCTsystems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc ). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0114] Further, unless otherwise noted, the use of the words “approximate,” “about,” “around,” “substantially,” etc., mean plus or minus ten percent.

[0115] Although the present embodiments have been particularly described with reference to preferred examples thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the present disclosure. It is intended that the appended claims encompass such changes and modifications.284902-1948-1444.1

Claims

Atty. Dkt. No. 102354-0797S24-137 PCTWHAT IS CLAIMED IS:

1. An electrolyte composition for a lithium-metal battery, the electrolyte composition comprising:a lithium compound; anda solvent selected from:an asymmetric non-fluorinated ether selected from 1,2-methoxy ethoxy ethane (EME), 1 -methoxy -2-propoxy ethane (MPE), l-methoxy-2-isopropoxy ethane (MiPE), and combinations thereof;a fluorinated asymmetric ether;a fluorinated asymmetric acetal; andcombinations thereof.

2. The electrolyte composition of claim 1, wherein the fluorinated asymmetric ether comprises a fluorinated EME selected from: l-methoxy-2-(2 -fluoroethoxy) ethane (F1EME); l-methoxy-2-(2,2-difluoroethoxy) ethane (F2EME); 1 -methoxy -2-(2, 2, 2-trifluoroethoxy) ethane (F3EME); and combinations thereof.

3. The electrolyte composition of claim 1 or claim 2, wherein the fluorinated EME comprises F3EME or F2EME.

4. The electrolyte composition of any one of claims 1-3, wherein the solvent comprises F3EME.

5. The electrolyte composition of any one of claims 1-4, wherein the solvent comprises MiPE, MPE, EME, or a combination thereof.

6. The electrolyte composition of any one of claims 1-5, wherein the solvent comprises EME.

7. The electrolyte composition of any one of claims 1-6, wherein the lithium compound comprises LiFSI.29S24-137 PCT I. Choi et al. Attv. Dkt 102354-0797 4902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT8. The electrolyte composition of any one of claims 1-7, wherein the lithium compound is present at a concentration of IM to 5M.

9. The electrolyte composition of any one of claims 1-8, wherein the lithium compound is present at a concentration of 1.5 M to 2.5 M.

10. The electrolyte composition of any one of claims 1-9, further comprising an electrolyte additive.

11. The electrolyte composition of claim 10, wherein the electrolyte additive comprises LiDFP.

12. The electrolyte composition of claim 10 or claim 11, wherein the electrolyte additive is present in the electrolyte composition at a concentration of about 0.5 wt.% to 5 wt.%.

13. A battery, comprising:a cathode current collector:a cathode in contact with the current collector;an anode, wherein the anode is opposite the cathode and comprises lithium metal; an anode current collector in contact with the anode; andthe electrolyte composition according to any one of claims 1-12 between the anode and the cathode.

14. The battery of claim 13, further comprising a separator between the anode and the cathode.

15. The battery of claim 13 or claim 14, wherein the solvent comprises F3EME.

16. The battery of any one of claims 13-15, wherein the lithium compound comprises LiFSI.304902-1948-1444.1Atty. Dkt. No. 102354-0797S24-137 PCT17. The battery of any one of claims 13-16, wherein the lithium compound is present in the electrolyte composition at a concentration of 1 M to 4 M.

18. The battery of any one of claims 13-17, wherein the lithium compound is present in the electrolyte composition at a concentration of 1.5 M to 2.5 M.

19. The battery of any one of claims 13-18, wherein the electrolyte composition further comprises LiDFP.

20. A method of making a battery, the method comprising:combining a lithium compound and a solvent to produce the electrolyte composition according to any one of claims 1-12;contacting a cathode with a cathode current collector;contacting an anode comprising Li metal with an anode current collector, the anode being opposite the cathode; anddisposing the electrolyte composition between the cathode and the anode to obtain the battery.314902-1948-1444.1

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