Halogenated phosphorus flame retardant additives for energy storage devices

Abstract

A nonaqueous electrolyte solution for an energy storage device is described. The solution includes i) an aprotic organic solvent system; ii) an alkali metal salt; and iii) at least one halogenated phosphorus-based flame retardant additive compound. The halogenated phosphorus-based flame retardant increases the flame retardancy of the nonaqueous electrolyte solution without appreciably impacting the electrochemical performance of the nonaqueous electrolyte solution. Methods and processes for making such nonaqueous electrolyte solutions are provided. Electrical energy storage devices with these enhanced properties, including enhanced flame retardancy, are also provided.

Description

HALOGENATED PHOSPHORUS FLAME RETARDANT ADDITIVES FOR ENERGYSTORAGE DEVICESCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 556,967, filed February 23, 2024, the disclosure of which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates generally to flame retardants for an electrical energy storage device and more particularly to such a device comprising a halogenated phosphorous flame retardant additive.BACKGROUND

[0003] One of the aspects impacting the safety of electrical energy storage devices is the uncontrolled release of energy leading to fires and explosions. A well-known example is a lithium-ion battery. Inclusion of a phosphorous containing halogenated flame retardant in the electrolyte is one way to mitigate the occurrence of fires or explosions caused by the release and ignition of flammable or combustible gasses or liquids from the device. For a flame retardant to be a suitable component of an energy storage device, it must not negatively affect its performance. Negative effects on device performance can include reduced conductivity, and / or chemical instability to the active material.

[0004] There is a need for fire safety solutions for energy storage devices that prevents or mitigates the magnitude of heat generation and damage caused by fires or explosions of these devices with minimal impact on device performance at a reasonable cost.SUMMARY

[0005] This summary lists several embodiments of the presently disclosed subject matter, and in many cases lists variations and permutations of these embodiments. This summary is merely exemplary of the numerous and varied embodiments. The mention of one or more representative features of a given embodiment is likewise exemplary. Such an embodiment can typically exist with or without the feature(s) mentioned;likewise, those features can be applied to other embodiments of the presently disclosed subject matter, whether listed in this summary or not. To avoid excessive repetition, this Summary does not list or suggest all possible combinations of such features.

[0006] In some embodiments, the presently disclosed subject matter provides an electrolyte for an energy storage device, wherein the electrolyte comprises: i) an electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated phosphorus-based flame retardant compound having a structure of Formula (I) or Formula (IV):ormu a , wherein, n is 1, 2, 3, 4, or 5; w is 0 or 1 ; x and y are each 0, 1, or 2, and z is 1, 2, or 3, wherein the sum of x, y, and z is 3;A is oxygen or sulfur;Z is oxygen, sulfur, or aliphatic carbon;L is oxygen, sulfur, or aliphatic carbon;Ri is an aliphatic or aliphatic ether group having 1-5 carbons;R2is an aliphatic or aliphatic ether group having 1-5 carbons; andR3 is an aliphatic group having 2-5 carbons, wherein said aliphatic group comprises at least one halogenated alkene group.

[0007] Thus, the electrolyte can include a halogenated phosphorus flame retardant comprising at least one halogenated phosphate or halogenated phosphonate. In some aspects, the electrolyte comprises a halogenated phosphorus flame retardant that includes a halogenated phosphate and / or a halogenated phosphonate compound comprising at least one halogen atom (e.g., at least one Br atom) in substitution of a hydrogen atom in an alkene group of a parent nonhalogenated phosphate or phosphate compound, where the parent nonhalogenated phosphate compound is selected from the group comprising diethyl prop-2-en-l-yl phosphate, ethenyl diethyl phosphate, ethenyl diethyl phosphate, ethenyl diethyl phosphate, ethyl methyl prop-2-en-l-yl phosphate, ethenyl ethyl methyl phosphate, and the parent nonhalogenated phosphonate compound is selected from the group comprising diethyl ethenylphosphonate, dimethyl ethenylphosphonate, diethyl prop-2-en-l-ylphosphonate, dimethyl prop-2-en-l- ylphosphonate, ethyl methyl ethenylphosphonate and ethyl methyl ethenylphosphonate.

[0008] The chemical structures for these halogenated phosphate and halogenated phosphonate compounds are as follows:wherein w is 1, 2, or 3, and each X is halogen (e.g., bromo).

[0009] In some embodiments, the halogenated flame retardant increases the flame retardancy in the electrolyte while minimally impacting the energy storage performance, as compared to an electrolyte without any halogenated phosphorous flame retardant.

[0010] In one embodiment, the electrolyte comprises a brominated phosphorus flame retardant comprising at least one brominated phosphate or brominated phosphonate. In some embodiments, the brominated phosphorus flame retardant comprises a brominated phosphate compound selected from the group comprising 2-bromo-2-propen-l-yl diethyl phosphate, 1 -bromoethenyl diethyl phosphate, 2-bromo-2-propen-l-yl dimethyl phosphate, 1 -bromoethenyl dimethyl phosphate, 2-bromo-2-propen-l-yl methyl ethyl phosphate, and 1 -bromoethenyl diethyl phosphate, and / or a brominated phosphonate compound selected from the group comprising diethyl (l-bromovinyl)phosphonate, dimethyl (I -bromo vinyl)phosphonate, diethyl (2-bromo-2-propenyl)phosphonate, dimethyl (2-bromo-2-propenyl)phosphonate, methyl ethyl (l-bromovinyl)phosphonate, methyl ethyl (2-bromo-2-propenyl)phosphonate, and dimethyl [(2£’)-3-bromopropy-2- en-l-yl]phosphonate. In some embodiments, the brominated flame retardant increases the flame retardancy in the electrolyte while minimally impacting the electrochemical performance of the electrolyte as compared to an electrolyte without any brominated phosphorous flame retardant.[Oil] In some embodiments, an electrolyte comprises a halogenated phosphorus flame retardant additive, an alkali metal salt, such as lithium, an additive, and an aprotic solvent for use in an electrochemical cell. In some embodiments, the electrolyte comprises an ionic liquid. In some embodiments, the ionic liquid comprises an organic cation and an inorganic / organic anion, with suitable organic cations including N-alkyl-N-alkyl- pyrrolidinium, N-alkyl-N-alkylpyridnium, N-alkyl-N-alkyl-sulfonium, N-alkyl-N- alkylammonium, N-alkyl-N-alkyl-piperdinium or the like, and suitable anions including tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, trifluoroacetate or the like. In some embodiments, the electrolyte comprises a polymer. The polymer in the electrolyte can include a poly(ethylene glycol) derivative, with varying molecular weights ranging from about 150 g / mol to about 10,000,000 g / mol. Suitable aprotic solvents include, for example, carbonates, ethers, acetamides, acetonitrile, symmetric sulfones, 1,3-dioxolanes, dimethoxy ethanes, glymes, siloxanes and their blends. The alkali metal salt can beselected from the group comprising LiBF4, LiNO3, LiPFe, LiAsIv,, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(pentafluoroethylsulfonyl)- imide, lithium trifluoroacetate, or a similar compound.In some embodiments, the electrolyte comprises a lithium salt in addition to the ionic liquid. A variety of lithium salts can be used, including, for example, Li[CF3CO2]; Li[C2F5CO2]; Li[C104J; Li[BF4]; Li[AsF6]; Li[PF6]; Li[PF2C2O4)2]; Li[PF4C2O4]; Li[CF3SO3]; Li[N(CP3SO2)2]; Li[C(CF3SO2)3]; Li[N(SO2C2F5)2]; lithium alkyl fluorophosphates; Li[B(C2O4)2]; Li[BF2C2O4]; Li2[Bi2Zi2 / H / ]; Li2[BioZio-yH / ]; or a mixture of any two or more thereof, wherein Z is independently at each occurrence a halogen, j is an integer from 0 to 12 and j' is an integer from 1 to 10.

[0012] In an embodiment of the present electrolyte, such as a formulation for a lithium- ion battery, aprotic solvents are combined with the present ionic liquids to decrease the viscosity and increase the conductivity of the electrolyte. The most appropriate aprotic solvents lack exchangeable protons, including cyclic carbonic acid esters, linear carbonic acid esters, phosphoric acid esters, oligoether substituted siloxanes / silanes, cyclic ethers, chain ethers, lactone compounds, chain esters, nitrile compounds, amide compounds, sulfone compounds, siloxanes, phosphoric acid esters, phosphates, phosphites, mono-, oligo-, or polyphosphazenes and the like. These solvents may be used singly, or at least two of them in admixture. Examples of aprotic solvents or carriers for forming the electrolyte systems include but are not limited to dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propylcarbonate, dipropyl carbonate, bis(trifluoroethyl) carbonate, bis (pentafluoropropyl) carbonate, trifluoroethyl methyl carbonate, pentafluoroethyl methyl carbonate, heptafluoropropyl methyl carbonate, perfluorobutyl methyl carbonate, trifluoroethylethyl carbonate, pentafluoroethyl ethylcarbonate, heptafluoropropyl ethyl carbonate, perfluorobutylethyl carbonate, etc., fluorinated oligomers, methyl propionate, ethyl propionate, butyl propionate, dimethoxyethane, triglyme, dimethylvinylene carbonate, tetraethyleneglycol, dimethyl ether, polyethylene glycols, triphenyl phosphate, tributyl phosphate, hexafluorocyclotriphosphazene, 2-ethoxy-2,4,4,6,6-pentafluoro-l,3,5,2-5,4- 5,6-5 triazatriphosphinine, triphenyl phosphite, sulfolane, dimethyl sulfoxide, ethyl methyl sulfone, ethylvinyl sulfone, allyl methylsulfone, divinyl sulfone, fluorophynelmethyl sulfone and gamma-butyrolactone.

[0013] In some embodiments, the electrolytes further include an additive to protect the electrodes from degradation. Thus, electrolytes of the presently disclosed subject matter can include an additive that is reduced or polymerized on the surface of a negative electrode to form a passivation film on the surface of the negative electrode. Likewise, electrolytes can include an additive that can be oxidized or polymerized on the surface of the positive electrode to form a passivation film on the surface of the positive electrode. In some embodiments, electrolytes of the presently disclosed subject matter can comprise mixtures of the two types of additives.

[0014] In some embodiments, the additive is a substituted or unsubstituted linear, branched or cyclic hydrocarbon including at least one oxygen atom and at least one aryl, alkenyl or alkynyl group. The passivating film formed from such additives can also be formed from a substituted aryl compound or a substituted or unsubstituted heteroaryl compound where the additive includes at least one oxygen atom.

[0015] Representative additives include, but are not limited to, glyoxal bis(diallylacetal), tetra(ethylene glycol) divinyl ether, l,3,5-triallyl-l,3,5-triazine- 2,4,6(lH,3H,5H)-trione, l,3,5,7-tetravinyl-l,3,5, 7-tetramethylcyclotetrasiloxane,2,4,6-triallyloxy-l,3,5-triazine, l,3,5-triacryloylhexahydro-l,3,5-triazine, 1,2-divinyl furoate, 1,3-butadiene carbonate, l-vinylazetidin-2-ne, l-vinylaziridin-2-one, 1- vinylpiperidin-2-one, l-vinylpyrrolidin-2-one, 2,4-divinyl-l,3-dioxane, 2-amino-3- vinylcyclohexanone, 2-amino-3-vinylcyclopropanone, 2-amino-4-vinylcyclobutanone, 2-amino-5-vinylcyclopentanone, 2-ary loxy-cyclopropanone, 2- vinyl- [1,2] oxazetidine, 2-vinylaminocyclohexanol, 2-vinylaminocyclopropanone, 2-vinyloxetane, 2-vinyloxy- cyclopropanone, 3-(N-vinylamino)cyclohexanone, 3,5-divinyl furoate, 3-vinylazetidin- 2-one, 3-vinylaziridin-2-one, 3-vinylcyclobutanone, 3-vinylcyclopentanone, 3- vinyloxaziridine, 3-vinyloxetane, 3-vinylpyrrolidin-2-one, 2-vinyl- 1,3 -dioxolane, acrolein diethyl acetal, acrolein dimethyl acetal, 4,4-divinyl-3-dioxolan-2-one, 4- vinyltetrahydropyran, 5-vinylpiperidin-3-one, allylglycidyl ether, butadiene monoxide, butyl-vinyl-ether, dihydropyran-3-one, divinyl butyl carbonate, divinyl carbonate, divinyl crotonate, divinyl ether, divinylethylene carbonate, divinyl ethylene silicate, divinylethylene sulfate, divinyl ethylene sulfite, divinyl methoxypyrazine, divinyl methylphosphate, divinyl propylene carbonate, ethyl phosphate, methoxy-o-terphenyl, methyl phosphate, oxetan-2-yl-vinylamine, oxiranylvinylamine, vinylcarbonate, vinylcrotonate, vinyl cyclopentanone, vinylethyl-2-furoate, vinyl ethylene carbonate, vinyl ethylene silicate, vinyl ethylene sulfate, vinyl ethylene sulfite, vinylmethacrylate, vinyl phosphate, vinyl-2-furoate, vinylcylopropanone, vinylethylene oxide, p-vinyl-y- butyrolactone or a mixture of any two or more thereof. In some embodiments, the additive may be a cyclotriphosphazene that is substituted with F, alkyloxy, alkenyloxy, aryloxy, methoxy, allyloxy groups or combinations thereof. For example, the additive may be a (divinyl)-(methoxy)(trifluoro)cyclotriphosphazene, (trivinyl)(difluoro)- (methoxy)cyclotriphosphazene, (vinyl)(methoxy)(tetrafluoro)cyclotriphosphazene, (aryloxy)(tetrafluoro)(methoxy)cyclotriphosphazene or (diaryloxy)(trifluoro)- (methoxy)cyclotriphosphazene compounds or a mixture of two or more such compounds. In some embodiments, the additive is vinyl ethylene carbonate, vinyl carbonate, or 1,2- diphenyl ether, or a mixture of any two or more such compounds.

[0016] Other representative additives include compounds with phenyl, naphthyl, anthracenyl, pyrrolyl, oxazolyl, furanyl, indolyl, carbazolyl, imidazolyl, thiophenyl, fluorinated carbonates, sultone, sulfide, anhydride, silane, siloxy, phosphate or phosphite groups. For example, additives include phenyl tri fluoromethyl sulfide, fluoroethylene carbonate, 1,3,2-dioxathiolane 2,2-dioxide, 1-propene 1,3-sultone, 1,3- propanesultone, l,3-dioxolan-2-one, 4-[ (2,2,2-trifluoroethoxy)methyl], l,3-dioxolan-2- one, 4-[[2,2,2-trifluoro-l-(trifluoromethyl)ethoxy]methyl]-, methyl 2,2,2- trifluoroethylcarbonate, nonafluorohexyltriethoxysilane, octamethyltrisiloxane, methyltris(trimethylsiloxy)silane, tetrakis(trimethylsiloxy)silane, (tridecafluoro- 1 , 1, 2, 2-tetrahydrooctyl)triethoxy silane, tris(lH, lH-heptafluorobutyl)phosphate, 3 ,3 ,3- trifluoropropyltris(3,3,3-trifluoropropyldimethylsiloxy)silane, (3 ,3 ,3- trifluoropropyl)trimethoxysilane, trimethylsilyl trifluoromethanesulfonate, tris(trimethylsilyl)borate, tripropyl phosphate, bis(trimethylsilylmethyl)benzylamine, phenyltris(trimethylsiloxy)silane, 1 ,3 bis(trifluoropropyl) tetramethyldisiloxane, triphenyl phosphate, tris(trimethylsilyl)phosphate, tris(lH, 1H, 5H- octafluoropentyl)phosphate, triphenyl phosphite, trilauryl trithiophosphite, tris(2,4-di- tert-butylphenyl) phosphite, tri-p-tolyl phosphite, tris(2,2,3,3,3- pentafluoropropyl)phosphate, succinic anhydride, 1,5,2,4-dioxadithiane 2, 2,4,4- tetraoxide, tripropyl trithiophosphate, aryloxpyrrole, aryloxy ethylene sulfate, aryloxypyrazine, aryloxy-carbazole trivinylphosphate, aryloxy-ethyl-2-furoate, aryloxy-o-terphenyl, aryloxypyridazine, butyl-aryloxy-ether, divinyl diphenyl ether, (tetrahydrofuran-2-yl)-vinylamine, divinyl methoxybipyridine, methoxy-4- vinylbiphenyl, vinyl methoxy carbazole, vinylmethoxy piperidine, vinyl methoxypyrazine, vinyl methyl carbonate-allylanisole, vinyl pyridazine, 1- divinylimidazole, 3-vinyltetrahydrofuran, divinyl furan, divinyl methoxyfuran, divinylpyrazine, vinyl methoxy imidazole, vinylmethoxypyrrole, vinyl-tetrahydrofuran, 2,4-divinyl isooxazole, 3,4 divinyl-1 -methyl pyrrole, aryloxyoxetane, aryloxy-phenyl carbonate, aryloxy-piperidine, aryloxytetrahydrofuran, 2-aryl-cyclopropanone, 2- diaryloxyfuroate, 4-allylanisole, aryloxy-carbazole, aryloxy-2-furoate, aryloxy- crotonate, aryloxy-cyclobutane, aryloxycyclopentanone, aryloxy-cyclopropanone, aryloxycycolophosphazene, aryloxy-ethylene silicate, aryloxyethylenesulfate, aryloxyethylene sulfite, aryloxyimidazole, aryloxy-methacrylate, aryloxy-phosphate, aryloxypyrrole, aryloxyquinoline, diaryloxycyclotriphosphazene, diaryloxy ethylene carbonate, diaryloxy furan, diaryloxymethyl phosphate, diaryloxy-butyl carbonate, diaryloxy- crotonate, diaryloxy-diphenyl ether, diaryloxy-ethylsilicate, diaryloxy-ethylene silicate, diaryloxy-ethylene sulfate, diaryloxyethylene sulfite, diaryloxy-phenyl carbonate, diaryloxy-propylene carbonate, diphenyl carbonate, diphenyl diaryloxy silicate, diphenyl divinyl silicate, diphenyl ether, diphenyl silicate, divinyl methoxydiphenyl ether, divinylphenyl carbonate, methoxycarbazole, or 2,4-dimethyl-6-hydroxy- pyrimidine, vinyl methoxyquinoline, pyridazine, vinyl pyridazine, quinoline, vinyl quinoline, pyridine, vinylpyridine, indole, vinyl indole, triethanolamine, 1,3- dimethylbutadiene, butadiene, vinyl ethylene carbonate, vinyl carbonate, imidazole, vinyl imidazole, piperidine, vinyl piperidine, pyrimidine, vinyl pyrimidine, pyrazine, vinyl pyrazine, isoquinoline, vinyl isoquinoline, quinoxaline, vinyl quinoxaline, biphenyl, 1,2-diphenyl ether, 1,2-diphenylethane, <?-terphenyl, N-methyl pyrrole, naphthalene or a mixture of any two or more such compounds.

[0017] In an embodiment, the electrolyte of the presently disclosed subject matter includes an aprotic gel polymer carrier / solvent. Suitable gel polymer carrier / solvents include polyethers, polyethylene oxides, polyimides, polyphosphazines, polyacrylonitriles, polysiloxanes, polyether grafted polysiloxanes, derivatives of the foregoing, copolymers of the foregoing, cross-linked and network structures of the foregoing, blends of the foregoing and the like, to which is added a suitable ionicelectrolyte salt. Other gel-polymer carrier / solvents include those prepared from polymer matrices derived from polypropylene oxides, polysiloxanes, sulfonated polyimides, perfluorinated membranes (e.g., resins sold under the tradename NAFION® (The Chemours Company FC, LLC, Wilmington, Delaware, United Staes of America), divinyl polyethylene glycols, polyethylene glycol-bis-(methyl acrylates), polyethylene glycol- bis(methyl methacrylates), derivatives of the foregoing, copolymers of the foregoing and cross-linked and network structures of the foregoing.

[0018] The halogenated phosphorus-based flame retardant additive materials have high solubility in organic solvents. Electrolyte solutions containing these halogenated phosphorous additive materials have high ionic conductivity and are suitable for use as an electrolytic solution for electrochemical devices. Examples of electrochemical devices are electric double-layer capacitor, secondary batteries, solar cells of the pigment sensitizer type, electrochromic devices and condensers, and this list is not limitative. Especially suitable as electrochemical devices are electric double-layer capacitor and secondary batteries, such as a lithium-ion battery.

[0019] In some embodiments, the presently disclosed subject matter provides an electrochemical device that comprises a cathode, an anode and an electrolyte comprising an ionic liquid as described herein. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the secondary battery is a lithium battery, a lithium-ion battery, a lithium-sulfur battery, a lithium-air battery, a sodium ion battery or a magnesium battery. In some embodiments, the electrochemical device is an electrochemical cell, such as a capacitor. In some embodiments, the capacitor is an asymmetric capacitor or supercapacitor. In some embodiments, the electrochemical cell is a primary cell. In some embodiments, the primary cell is a lithium / MnCh battery or Li / poly(carbon mono fluoride) battery. In some embodiments, the electrochemical cell is a solar cell.

[0020] Also provided herein is an energy storage device that comprises a cathode, an anode, and an electrolyte comprising a halogenated phosphorous-based flame retardant.

[0021] In some embodiments, suitable cathodes include those such as, but not limited to, a lithium metal oxide, spinel, olivine, carbon-coated olivine, LiFePCL, LiCoCL, LiNiCL, LiNii Coj>Met-O2, LiMno.5Nio.5O2, LiMno.3Coo.3Nio.3O2, LiMn2O4, LiFeO2, Li i+ ’NiaMnpCoyMet'sOz-.-:’, Fz’, A / E^XO^s (e.g., NASICON), vanadium oxide, lithiumperoxide, sulfur, polysulfide, a lithium carbon mono fluoride or mixtures of any two or more thereof, where Met is Al, Mg, Ti, B, Ga, Si, Mn or Co; Met' is Mg, Zn, Al, Ga, B, Zr or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu or Zn; B is Ti, V, Cr, Fe or Zr; X is P, S, Si, W or Mo; and wherein 0<x<0.3, 0<y<0.5, 0<z<0.5, 0<x'<0.4, 0<a<l, 0<P<l, 0<y<l, 0<8<0.4, 0<z'<0.4 and 0<h'<3.

[0022] In some embodiments, suitable anodes include those such as lithium metal, graphitic materials, amorphous carbon, Li^isO , tin alloys, silicon alloys, intermetallic compounds or mixtures of any two or more such materials. Suitable graphitic materials include natural graphite, artificial graphite, graphitized mesa-carbon micro beads (MCMB) and graphite fibers, as well as any amorphous carbon materials. In some embodiments, the anode and cathode are separated from each other by a porous separator.

[0023] The separator for the lithium battery often is a microporous polymer film. Examples of polymers for forming films include: nylon, cellulose, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, polybutene, or co-polymers or blends of any two or more such polymers. In some instances, the separator is an electron beam-treated microporous polyolefin separator. The electron beam treatment can improve the deformation temperature of the separator and can accordingly enhance the high temperature performance of the separator. Additionally or alternatively, the separator can be a shut-down separator. The shut-down separator can have a trigger temperature above about 130° C. to permit the electrochemical cells to operate at temperatures up to about 130° C.

[0024] The disclosure will be further illustrated with reference to the following specific examples. It is understood that these examples are given by way of illustration and are not meant to limit the disclosure or the claims to follow.

[0025] In some embodiments, an energy storage device comprises a lithium battery, lithium-ion battery, lithium-sulfur battery, lithium-air battery, sodium ion battery, magnesium battery, electrochemical cell, capacitor, lithium / MnCL battery, Li / poly(carbon monofluoride) battery, or solar cell.

[0026] In some embodiments, the cathode and anode of an energy storage device is separated by porous separator. Embodiments of porous separators include an electronbeam-treated micro-porous polyolefin separator or a microporous polymer film comprising nylon, cellulose, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, polybutene, or co-polymers or blends of any two or more such polymers.

[0027] In another aspect, provided herein is a process for producing an electrolyte for an energy storage device, which process includes combining: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated phosphorus-based flame retardant as disclosed herein.

[0028] These and other objects are achieved in whole or in part by the presently disclosed subject matter. Other objects and advantages of the presently disclosed subject matter will become apparent to those skilled in the art after a study of the following description, Drawings and Examples.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0029] The presently disclosed subject matter can be better understood by referring to the following figures. The drawings are not intended to limit the scope of this presently disclosed subject matter, which is set forth with particularity in the claims as appended or as subsequently amended, but merely to clarify and exemplify the presently disclosed subject matter.

[0030] For a more complete understanding of the presently disclosed subject matter, reference is now made to the following figures.

[0031] FIG. 1 A is a graphical depiction of thermal ramp abuse testing results evaluating the flammability of nonaqueous electrolyte solutions without the disclosed halogenated phosphorus flame retardants.

[0032] FIG. IB Flammability testing for an electrolyte solution comprising 13 wt% diethyl (1 -bromovinyljphosphonate.

[0033] FIG. 2A Flammability testing for an electrolyte solution comprising 10 wt% Hishicolin-O.

[0034] FIG. 2B Flammability testing for an electrolyte solution comprising 13 wt% diethyl ( 1 -b romov i ny 1 )ph o sphon ate .

[0035] FIG. 3 Structure of diethyl 2-bromoethylphosphonate, a halogenated additive used in a comparative electrolyte solution.

[0036] FIG. 4 Results of Coulombic Efficiency measurements up to 10 cycles.DETAILED DESCRIPTION

[0037] I. Definitions

[0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the presently disclosed subject matter.

[0039] While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.

[0040] All technical and scientific terms used herein, unless otherwise defined below, are intended to have the same meaning as commonly understood by one of ordinary skill in the art. References to techniques employed herein are intended to refer to the techniques as commonly understood in the art, including variations on those techniques or substitutions of equivalent techniques that would be apparent to one of skill in the art. While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.

[0041] Components referred to by chemical name or formula anywhere in the specification or claims hereof, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type (e.g., another component, a solvent, or etc.). It matters not what chemical changes, transformations and / or reactions, if any, take place in the resulting mixture or solution as such changes, transformations, and / or reactions are the natural result of bringing the specified components together under the conditions called for pursuant to this disclosure. Thus, the components are identified as ingredients to be brought together in connection with performing a desired operation or in forming a desired composition. Also, even though the claims hereinafter may refer to substances, components and / or ingredients in the present tense ("comprises", "is", etc.), the reference is to the substance, component or ingredient as it existed at the time just before it wasfirst contacted, blended or mixed with one or more other substances, components and / or ingredients in accordance with the present disclosure. The fact that a substance, component or ingredient may have lost its original identity through a chemical reaction or transformation during the course of contacting, blending or mixing operations, if conducted in accordance with this disclosure and with ordinary skill of a chemist, is thus of no practical concern.

[0042] In describing the presently disclosed subject matter, it will be understood that a number of techniques and steps are disclosed. Each of these has individual benefit and each can also be used in conjunction with one or more, or in some cases all, of the other disclosed techniques.

[0043] Accordingly, for the sake of clarity, this description will refrain from repeating every possible combination of the individual steps in an unnecessary fashion. Nevertheless, the specification and claims should be read with the understanding that such combinations are entirely within the scope of the present disclosure and the claims.

[0044] Following long-standing patent law convention, the terms “a”, “an”, and “the” refer to “one or more” when used in this application, including the claims. Thus, for example, reference to "a cell" includes a plurality of such cells, and so forth.

[0045] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0046] As used herein, the term “about,” when referring to a value or to an amount of a composition, dose, mass, weight, temperature, time, volume, concentration, percentage, etc., is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed methods or employ the disclosed compositions.

[0047] The term “comprising”, which is synonymous with “including” “containing” or “characterized by” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. “Comprising” is a term of art used in claim language which means that the named elements are essential, but other elements can be added and still form a construct within the scope of the claim.

[0048] As used herein, the phrase “consisting of’ excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0049] As used herein, the phrase “consisting essentially of’ limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

[0050] With respect to the terms “comprising”, “consisting of”, and “consisting essentially of’, where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

[0051] As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D.

[0052] The term “aliphatic” as used herein indicates a linear, branched or cyclic nonaromatic hydrocarbyl group, which can include alkyl, alkenyl, and alkynyl bonds. Nonlimiting examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, cyclobutyl, cyclopentyl, and unsaturated versions thereof (e.g., propenyl, etc.).

[0053] The term “aliphatic ether” as used herein indicates a linear, branched or cyclic non-aromatic hydrocarbyl group that has an oxygen atom inserted between carbon atoms of the non-aromatic hydrocarbyl group to form an ether linkage as part of the hydrocarbyl unit. Non-limiting examples include methyoxymethyl, methoxyethyl, methoxypropyl, ethoxymethyl, ethoxyethyl, propoxyethyl, and the like.

[0054] The term “alkyl” as used herein refers to a saturated linear or branched hydrocarbyl group, e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, etc. In some embodiments, “alkyl” refers to an alkyl group with 1 to 5 carbons.

[0055] The terms “alkene” and “alkenyl” as used herein refer to an aliphatic group containing at least one carbon-carbon double bond.

[0056] The terms “halo”, “halide”, and “halogen” as used herein refer to an atom of the element fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0057] The term “halogenated alkene group’’ as used herein refers to a group having a structure selected from:each X is halogen.

[0058] II. Halogenated Phosphorus-Based Flame Retardants for Electrical Energy Storage Devices

[0059] According to some aspects, the presently disclosed subject matter provides an electrolyte for an energy storage device which contains a halogenated phosphorus-based flame retardant additive whose molecular structure comprises at least one halogen atom and one phosphorous atom. In some aspects, the flame retardant additive comprises a halogenated (e.g., brominated) phosphate or a halogenated (e.g., brominated) phosphonate. While not wanting to be limited to any single theory, the presence of the halogenated phosphorus-based flame retardant additive of the presently disclosed subject matter can minimize the release of heat energy arising from the conversion of electrical energy to heat. The conversion of electrical energy into heat energy can result in fires and explosions which can also be mitigated by the presence of the flame retardant additive according to the presently disclosed subject matter. Surprisingly, addition of the presently disclosed flame retardant additives can provide acceptable electrical storage performance of the electrical devices provided by this disclosure.

[0060] In some aspects, the halogenated phosphorus-based flame retardant comprises a compound having a structure of Formula (I) or Formula (IV):wherein, n is 1, 2, 3, 4, or 5; w is 0 or 1; x and y are each 0, 1, or 2, and z is 1, 2, or 3, wherein the sum of x, y, and z is 3; A is oxygen or sulfur; Z is oxygen, sulfur, or aliphatic carbon; L is oxygen, sulfur, or aliphatic carbon; Ri is an aliphatic or aliphatic ether group having 1-5 carbons; R is an aliphatic or aliphatic ether group having 1-5 carbons; and Rj is an aliphatic group having 2-5 carbons, wherein said aliphatic group comprises at least one halogenated alkene group.

[0061] In some embodiments, A is oxygen (i.e., -O-).

[0062] In some embodiments, Z is oxygen (i.e., -O-) or aliphatic carbon (e.g., -CH2-).In some embodiments, Z is oxygen.

[0063] In some embodiments, w is 1. In some embodiments, L is oxygen (i.e., -O-) or aliphatic carbon (e.g., -CH2-). In some embodiments, L is oxygen. In some embodiments, w is 0 and L is not present.

[0064] In some embodiments, R3 is a brominated alkene group (i.e., a halogenated alkene group comprising at least one Br group). Thus, in some embodiments, the halogenated phosphorus-based flame retardant is a brominated phosphorus-based compound.

[0065] Brominated phosphonates and phosphates of the presently disclosed subject matter were evaluated as flame retardants in various electrolyte blends which may find use in energy storage devices. It is believed that there is a synergy between bromine andphosphorous. For example, with an amount of phosphorus present, as discussed herein, less bromine is needed for an effective system than if it were to be an all-bromine flame retardant.

[0066] Throughout this document, the term electrolyte is used interchangeably with the phrases “liquid electrolyte medium”, "electrolyte solution" and “nonaqueous electrolyte solution." The electrolyte may contain one or more solvents that typically form the liquid electrolyte medium of energy storage devices, which includes solvents that are polar and aprotic, stable to electrochemical cycling, and preferably have low viscosity. These solvents usually include noncyclic carbonic acid esters, cyclic carbonic acid esters, ethers, sulfur-containing compounds, and esters of boric acid. Further, the electrolyte may contain one or more alkali salt, such as a lithium salt.

[0067] Throughout this document, the terms “halogenated phosphorus flame retardant” and “halogenated phosphorus-based flame retardant” are used interchangeably with “halogenated phosphorous additive,” “halogenated phosphorous compound,” or “halogenated flame retardant.”

[0068] Throughout this document, the term “flame retardant,” includes or encompasses any properties which prevent flames or fire, extinguish flames or fire, delay the onset of flames or fire, reduce the energy released by flames or fire, or reduce the release of heat energy stored as electrical energy in an electrical energy storage device. Moreover, the term “flame retardancy” applies to the suppression of combustion whether in flaming combustion as in a fire or smoldering combustion in the condensed or solid phase without a flame; or the suppression of the conversion of stored electrical energy into fuel. This applies to the combustion of combustible or flammable organic, organometallic, or inorganic materials. Moreover, this applies to combustible or flammable materials in vapor, gas, liquid, solid, or any combination of these phases.

[0069] The solvents that can form the liquid electrolyte medium in the practice of the present disclosure include aprotic organic solvents comprising an open-chain or cyclic carbonate, carboxylic acid ester, nitrile, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono-, oligo-, or polyphosphazene or mixtures thereof.

[0070] In some embodiments, preferred solvents include ethylene carbonate (1,3- dioxolan-2-one), dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate,dioxolane, dimethoxy ethane (glyme), tetrahydrofuran, ethylene sulfite, 1,3-propylene glycol boric ester, and mixtures of any two or more of the foregoing. In other embodiments, preferred solvents include ethylene carbonate, ethyl methyl carbonate, and mixtures thereof. More preferred are mixtures of ethylene carbonate and ethyl methyl carbonate, especially at volume ratios of ethylene carbonate:ethyl methyl carbonate ratios of about 20:80 to about 40:60, more preferably about 25:75 to about 35:65.

[0071] Suitable cations of the alkali metal salt in the practice of the presently disclosed subject matter include lithium, sodium, aluminum, or magnesium. In some embodiments, these include lithium chloride, lithium bromide, lithium iodide, lithium perchlorate, lithium nitrate, lithium thiocyanate, lithium aluminate, lithium tetrachloroaluminate, lithium tetrafluoroaluminate, lithium tetraphenylborate, lithium tetrafluoroborate, lithium bis(oxalato)borate (LiBOB), lithium di(fluoro)(oxalato)borate (LiDFOB), lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium titanium oxide, lithium manganese oxide, lithium cobalt oxide (LiCoCh), lithium nickel oxide (LiNiCh), lithium alkyl carbonates in which the alkyl group has 1 to 6 carbon atoms, lithium methyl sulfonate, lithium trifluoromethyl sulfonate, lithium pentafluoroethyl sulfonate, lithium pentafluorophenylsulfonate, lithium fluorosulfonate, lithium bis(trifluoromethy 1 sulfony 1 jimide, lithium bis(pentafluoroethy 1 sulfo ny 1 jimide, lithium (ethylsulfonyl)(trifluoromethylsulfonyl)imide, and mixtures of any two or more of the foregoing.

[0072] Typical concentrations for the lithium-containing salt in the electrolyte solution are in the range of about 0.1 M to about 2.5 M, preferably about 0.5 M to about 2 M, more preferably about 0.75 M to about 1.75 M, and still more preferably about 0.95 M to about 1.5 M. In some embodiments, when more than one lithium-containing salt forms the lithium-containing electrolyte, the concentration refers to the total concentration of all of the lithium-containing salts present in the electrolyte solution.

[0073] In some aspects, the electrolyte can contain other salts in addition to lithium salts, unless such other salt(s) materially degrade either the performance of the battery for the desired application, or the flame retardancy of the electrolyte solution. Suitable electrolytes other than lithium salts include, but are not limited to, other alkali metal salts, e.g., sodium salts, potassium salts, rubidium salts, and cesium salts, and alkalineearth metal salts, e.g., magnesium salts, calcium salts, antimony salts, strontium salts, and barium salts. In some aspects, the salts in the non-aqueous electrolyte solution are only one or more lithium salts.

[0074] Suitable alkali metal salts that can be present in the electrolyte include, but are not limited to, sodium salts such as sodium chloride, sodium bromide, sodium iodide, sodium perchlorate, sodium nitrate, sodium thiocyanate, sodium aluminate, sodium tetrachloroaluminate, sodium tetrafluoroaluminate, sodium tetraphenylborate, sodium tetrafluoroborate, and sodium hexafluorophosphate; and potassium salts such as potassium chloride, potassium bromide, potassium iodide, potassium perchlorate, potassium nitrate, potassium thiocyanate, potassium aluminate, potassium tetrachloroaluminate, potassium tetrafluoroaluminate, potassium tetraphenylborate, potassium tetrafluoroborate, and potassium hexafluorophosphate.

[0075] Suitable alkaline earth metal salts that can be present in the electrolyte include, but are not limited to, magnesium salts such as magnesium chloride, magnesium bromide, magnesium iodide, magnesium perchlorate, magnesium nitrate, magnesium thiocyanate, magnesium aluminate, magnesium tetrachloroaluminate, magnesium tetrafluoroaluminate, magnesium tetraphenylborate, magnesium tetrafluoroborate, and magnesium hexafluorophosphate; and calcium salts such as calcium chloride, calcium bromide, calcium iodide, calcium perchlorate, calcium nitrate, calcium thiocyanate, calcium aluminate, calcium tetrachloroaluminate, calcium tetrafluoroaluminate, calcium tetraphenylborate, calcium tetrafluoroborate, and calcium hexafluorophosphate.

[0076] In an embodiment of the presently disclosed subject matter, the flameretardant is soluble in, or miscible with, the liquid medium of the nonaqueous electrolyte solution. Flame retardants that are in liquid form are miscible with the liquid medium of the nonaqueous electrolyte solution, where "miscible" means that the flame retardants do not form a separate phase from the electrolyte solution. More specifically, in some embodiments a flame retardant is miscible if it forms a single phase in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate which contains 1.2 M lithium hexafluorophosphate.

[0077] The term "soluble," usually used for flame retardants in solid form, indicates that, once dissolved, the flame retardant does not precipitate from, or form a suspension or slurry in, the nonaqueous electrolyte solution. More specifically, in someembodiments a flame retardant is soluble if it dissolves in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate which contains 1.2 M lithium hexafluorophosphate, after 24 hours of shaking in a mechanical shaker, if no precipitate, suspension, or slurry is formed after the shaking is stopped. In one embodiment of the presently disclosure, it is preferred that the halogenated phosphorus flame retardant does not cause the precipitation of, or formation of a suspension or slurry of, any of the other components of the nonaqueous electrolyte solution.

[0078] In one embodiment of the practice of the presently disclosed subject matter, the concentration of brominated phosphorous flame retardants combined with electrolyte generally have a bromine content of 0.01 - 20% of the total electrolyte composition. In another embodiment, about 3 wt% or more of the total electrolyte, preferably about 5 wt% or more, based on the weight of the brominated flame retardant and a boiling point of about 60°C or higher, preferably about 65°C or higher, more preferably about 85°C or higher. In some embodiments, the brominated flame retardants in the practice of the presently disclosed subject matter have a bromine content in the molecule that ranges from about 15 wt% to about 80 wt%, more preferably about 20 wt% to about50 wt%. In some preferred embodiments, the brominated flame retardants have a bromine content in the molecule that ranges from about 25 wt% to about 35 wt%. Moreover, in some embodiments the phosphorus content in the molecule can range from about 3 wt% to about 20 wt%. In the practice of the presently disclosed subject matter, a flame retardant amount in the nonaqueous electrolyte solution means a concentration sufficient to cause a desired level of flame retardancy. One method for screening or approximating the flame retardant loading necessary to extinguish a liquid electrolyte solution is the modified horizontal UL-94 test described below. The flame retardant loading can vary based on the particular halogenated phosphorus flame retardant(s) used, and in some embodiments is usually more than about 8 wt% flame retardant molecules, preferably about 10 wt% or more flame retardant molecules, relative to the total weight of a nonaqueous electrolyte solution. In other embodiments, the flame retardant amount is more than about 10 wt% flame- retardant molecules, or more than about 13 wt% flame retardant molecules, and preferably about 13 wt% relative to the total weight of the nonaqueous electrolyte solution.

[0079] In one embodiment, the flame retardant amount in the nonaqueous electrolyte solution (that passes the modified horizontal UL-94 test described below) on the basis of bromine content is usually about 2 wt% or more bromine (atoms), relative to the total weight of the nonaqueous electrolyte solution and is different for different brominated flame retardants. In some embodiments, the flame retardant amount is about 2 wt% or more, preferably about 3 wt% or more, bromine (atoms), relative to the total weight of the nonaqueous electrolyte solution. In other embodiments, the flame retardant amount is about 2 wt% or more, preferably about 3 wt% or more, more preferably about 4 wt% or more, bromine (atoms), relative to the total weight of the nonaqueous electrolyte solution.

[0080] In some embodiments, mixtures of two or more halogenated phosphorus-based flame retardants or halogenated phosphorus flame retardants with other halogenated flame retardants can be used in the practice of the presently disclosed subject matter. In the mixtures of two or more halogenated flame retardants, the flame retardant amount is about 5 wt% or more, about 10 wt% or more, or about 15 wt% or more flame retardant molecules relative to the total weight of the nonaqueous electrolyte solution, where the amount refers to the total amount of halogenated phosphorus flame retardants, halogenated flame retardants, or mixtures thereof in a nonaqueous electrolyte solution. Similarly, in one embodiment, the flame retardant amount of bromine is about 2 wt% or more, about 3 wt% or more, about 4 wt% or more bromine (atoms), relative to the total weight of the nonaqueous electrolyte solution, where the amount refers to the total amount of bromine atoms from all of the brominated phosphorus flame retardants or other combined brominated flame retardants in the nonaqueous electrolyte solution.

[0081] In some embodiments of the present disclosure, at least one electrochemical additive is included in the nonaqueous electrolyte solution. In the practice of the presently disclosed subject matter, the electrochemical additives are soluble in, or miscible with, the liquid medium of the nonaqueous electrolyte solution. Electrochemical additives that are in liquid form are miscible with the liquid medium of the nonaqueous electrolyte solution, where "miscible" means that the electrochemical additives do not form a separate phase from the electrolyte solution. More specifically, by way of example and not limitation, an electrochemical additive is miscible if it forms a single phase in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methylcarbonate which contains 1.2 M lithium hexafluorophosphate, after 24 hours of shaking in a mechanical shaker, and no separate phase is formed after the shaking is stopped, and the electrochemical additive does not precipitate from, or form a suspension or slurry in, the nonaqueous electrolyte solution.

[0082] The term "soluble," usually used for electrochemical additives in solid form, indicates that, once dissolved, the electrochemical additive does not precipitate from, or form a suspension or slurry in, the nonaqueous electrolyte solution. More specifically, by way of example and not limitation, an electrochemical additive is soluble if it dissolves in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate which contains 1.2 M lithium hexafluorophosphate, after 24 hours of shaking in a mechanical shaker, if no precipitate, suspension, or slurry is formed after the shaking is stopped. It is recommended and preferred that the halogenated phosphorus flame retardant does not cause the precipitation of, or formation of a suspension or slurry of, any of the other components of the nonaqueous electrolyte solution.

[0083] The halogenated phosphorus flame retardant, electrochemical additive, and mixtures thereof are generally stable to electrochemical cycling, and preferably have low viscosities and / or do not significantly increase the viscosity of the nonaqueous electrolyte solution.

[0084] In various embodiments, the electrochemical additive comprises a sulfur- containing compound, phosphorus-containing compound, boron-containing compound, silicon-containing compound, fluorine-containing compound, nitrogen containing compound, compound containing at least one unsaturated carbon-carbon bond, carboxylic acid anhydride or the mixtures thereof. In some embodiments, the electrochemical additive is selected from a) unsaturated cyclic carbonates containing three to about four carbon atoms, b) fluorine- containing saturated cyclic carbonates containing three to about four carbon atoms and one to about two fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about six carbon atoms, d) trihydrocarbyl phosphates containing three to about nine carbon atoms, e) cyclic sultones containing three to about four carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered ring and containing two to about four carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5 -membered ring and containing two to about four carbon atoms, h) cyclic dioxadithio poly oxide compounds having a 6- membered or 7-membered ring and containing two to about four carbon atoms, i) another lithium- containing salt, and j) mixtures of any two or more of the foregoing.

[0085] In other embodiments, the electrochemical additive is selected from a) an unsaturated cyclic carbonate in an amount of about 0.5 wt% to about 12 wt%, relative to the total weight of the nonaqueous electrolyte solution, b) a fluorine-containing saturated cyclic carbonate in an amount of about 0.5 wt% to about 8 wt%, relative to the total weight of the nonaqueous electrolyte solution, c) a tris(trihydrocarbylsilyl) phosphite in an amount of about 0.1 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, d) a trihydrocarbyl phosphate in an amount of about 0.5 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, e) a cyclic sultone in an amount of about 0.25 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, f) a saturated cyclic hydrocarbyl sulfite in an amount of about 0.5 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, g) a saturated cyclic hydrocarbyl sulfate in an amount of about 0.25 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, h) a cyclic dioxadithio polyoxide compound in an amount of about 0.5 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, i) another lithium-containing salt in an amount of about 0.5 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution, and j) mixtures of any two or more of the foregoing.

[0086] In some embodiments, the electrochemical additive is an unsaturated cyclic carbonate containing three to about six carbon atoms, preferably three to about four carbon atoms. Suitable unsaturated cyclic carbonates include vinylene carbonate (1,3- dioxol-2- one), 4-methyl- 1 ,3-dioxol-2-one, and 4,5-dimethyl-l ,3-dioxol-2-one; vinylene carbonate is a preferred unsaturated cyclic carbonate. The unsaturated cyclic carbonate is preferably in an amount of about 0.5 wt% to about 12 wt%, more preferably about 0.5 wt% to about 3 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0087] When the electrochemical additive is a fluorine-containing saturated cyclic carbonate containing three to about five carbon atoms, preferably three to about four carbon atoms, and one to about four fluorine atoms, preferably one to about two fluorine atoms, suitable fluorine-containing saturated cyclic carbonates include 4-fluoro-ethylene carbonate and 4,5-difluoro-ethylene carbonate. Preferably the fluorine-containingsaturated cyclic carbonate is 4-fluoro-ethylene carbonate. The fluorine-containing saturated cyclic carbonate is preferably in an amount of about 0.5 wt% to about 8 wt%, more preferably about 1.5 wt% to about 5 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0088] The tris(trihydrocarbylsilyl) phosphite electrochemical additives contain three to about nine carbon atoms, preferably about three to about six carbon atoms; the trihydrocarbylsilyl groups may be the same or different. Suitable tris(trihydrocarbylsilyl) phosphites include tris(trimethylsilyl) phosphite, bis(trimethylsilyl)(triethylsilyl) phosphite, tris(triethylsilyl) phosphite, bis(trimethylsilyl)(triethylsilyl) phosphite, bis(trimethylsilyl)(tri-n-propylsilyl)phosphite, and tris(tri-n-propylsilyl) phosphite; tris(trimethylsilyl) phosphite is a preferred tris(trihydrocarbylsilyl) phosphite. The tris(trihydrocarbylsilyl) phosphite is preferably in an amount of about 0.1 wt% to about 5 wt%, more preferably about 0.15 wt% to about 4 wt%, even more preferably about 0.2 wt% to about 3 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0089] In some embodiments, the electrochemical additive is a trihydrocarbyl phosphate containing three to about twelve carbon atoms, preferably three to about nine carbon atoms. The hydrocarbyl groups can be saturated or unsaturated, and the hydrocarbyl groups in the trihydrocarbyl phosphate may be the same or different. Suitable trihydrocarbyl phosphates include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, tri-n-propyl phosphate, triallyl phosphate, and trivinyl phosphate; triallyl phosphate is a preferred trihydrocarbyl phosphate. The trihydrocarbyl phosphate is usually in an amount of about 0.5 wt% to about 5 wt%, preferably about 1 wt% to about 5 wt%, more preferably about 2 wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0090] When the electrochemical additive is a cyclic sultone containing three to about eight carbon atoms, preferably three to about four carbon atoms, suitable cyclic sultones include 1,3-propane sultone, 1,3-propene sultone, 1,3-butane sultone (5 -methyl- 1,2- oxathiolane 2,2-dioxide), 2,4-butane sultone (3 -methyl- 1,2-oxathiolane 2,2-dioxide), 1,4- butane sultone (1,2-oxathiane 2,2-dioxide), 2-hydroxy-alpha-toluenesulfonic acid sultone (3H-l,2-benzoxathiole 2,2-dioxide), and 1,8-naphthosultone; preferred cyclic sultones include 1,3-propane sultone and 1,3-propene sultone. The cyclic sultone ispreferably in an amount of about 0.25 wt% to about 5 wt%, more preferably about 0.5 wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0091] The saturated cyclic hydrocarbyl sulfite electrochemical additive contains two to about six carbon atoms, preferably two to about four carbon atoms, and has a 5- membered or 6-membered ring, preferably a 5-membered ring. One or more substituents can be present on the ring, such as methyl or ethyl groups, preferably one or more methyl groups, more preferably, no substituents are present on the ring. Suitable saturated cyclic hydrocarbyl sulfites include 1,3,2-dioxathiolane, 2-oxide (1,2-ethylene sulfite), 1,2- propanediol sulfite (1,2-propylene sulfite), 4,5-dimethyl-l,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiane 2-oxide, 4-methyl-l,3-dioxathiane, 2-oxide (1,3-butylene sulfite); preferred cyclic hydrocarbyl sulfites include 1,3,2-dioxathiolane, 2-oxide (1,2-ethylene sulfite). The cyclic hydrocarbyl sulfite is preferably in an amount of about 0.5 wt% to about 5 wt%, more preferably about 1 wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0092] In some embodiments, the electrochemical additive is a saturated cyclic hydrocarbyl sulfate containing two to about six carbon atoms, preferably two to about four carbon atoms, and has a 5-membered or 6-membered ring, preferably a 5-membered ring. One or more substituents can be present on the ring, such as methyl or ethyl groups, preferably one or more methyl groups. Suitable saturated cyclic hydrocarbyl sulfates include 1,3,2-dioxathiolane 2,2- dioxide (1,2-ethylene sulfate), 1,3,2-dioxathiane 2,2- dioxide (1,3 -propylene sulfate), 4- methyl- 1,3,2-dioxathiane 2,2-dioxide (1,3-butylene sulfate), and 5, 5 -dimethyl- 1,3,2-dioxathiane 2,2-dioxide. The saturated cyclic hydrocarbyl sulfate is preferably in an amount of about 0.25 wt% to about 5 wt%, more preferably about 1 wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0093] When the electrochemical additive is a cyclic dioxadithio polyoxide compound, the cyclic dioxadithio polyoxide compound contains two to about six carbon atoms, preferably two to about four carbon atoms, and has 6-membered, 7-membered, or 8- membered ring. Preferably, the cyclic dioxadithio polyoxide compound contains two to about four carbon atoms, and has 6-membered or 7-membered ring. One or more substituents can be present on the ring, such as methyl or ethyl groups, preferably one or more methyl groups, more preferably, no substituents are present on the ring. Suitablecyclic dioxadithio polyoxide compounds include 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide,1.5.2.4-dioxadithiepane 2,2,4,4-tetraoxide (cyclodisone), 3-methyl-l,5,2,4- dioxadithiepane, 2,2,4,4-tetraoxide, and 1,5,2,4-dioxadithiocane, 2,2,4,4-tetraoxide;1.5.2.4-dioxadithiane 2,2,4,4-tetroxide is preferred. The cyclic dioxadithio polyoxide compound is preferably in an amount of about 0.5 wt% to about 5 wt%, more preferably about 1 wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0094] The phrases "another lithium-containing salt" and "other lithium containing salt" indicate that there are at least two lithium salts used in the preparation of the electrolyte solution. When the electrochemical additive is another lithium-containing salt, it is preferably in an amount of about 0.5 wt% to about 5 wt% relative to the total weight of the nonaqueous electrolyte solution. Suitable lithium-containing salts include all of the lithium-containing salts listed above.

[0095] Mixtures of any two or more of the foregoing electrochemical additives can be used, including different electrochemical additives of the same type and / or electrochemical additives of different types. When mixtures of electrochemical additives are used, the combined amount of the electrochemical additives is about 0.25 wt% to about 5 wt% relative to the total weight of the nonaqueous electrolyte solution. Mixtures of an unsaturated cyclic carbonate and a saturated cyclic hydrocarbyl sulfite or mixtures of a cyclic sultone, a tris(trihydrocarbylsilyl) phosphite, and a cyclic dioxadithio polyoxide compound are preferred.

[0096] Additional ingredients that are often included in electrolyte solutions for lithium-ion batteries can also be present in the electrolyte solutions of the present disclosure. Such additional ingredients include succinonitrile and silazane compounds such as hexamethyldisilazane. Typically, the amount of an optional ingredient is in the range of about 1 wt% to about 5 wt%, preferably about 2 wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution.

[0097] Another embodiment of the presently disclosed subject matter provides a method or process for producing a nonaqueous electrolyte solution for a lithium-ion battery. The process comprises combining components comprising i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated phosphorus flame retardant as disclosed herein. Optionally, in some embodiments the components furthercomprise iv) at least one electrochemical additive as described herein. The halogenated phosphorus flame retardant is present in the electrolyte solution in an amount sufficient to cause flame retardancy. More particularly, in some embodiments of the disclosed process for producing a nonaqueous electrolyte solution for a lithium-ion battery the at least one halogenated phosphorus flame retardant is added at more than about 8 wt% flame retardant molecules, preferably about 10 wt% or more flame retardant molecules, relative to the total weight of the nonaqueous electrolyte solution. In other embodiments, the flame retardant amount is more than about 8 wt% flame retardant molecules, more than 10 wt% flame retardant molecules, more than about 13 wt% flame retardant molecules relative to the total weight of the nonaqueous electrolyte solution.

[0098] In such processes and methods, the ingredients can be combined in any order, although it is preferable to add all of the components to the liquid electrolyte medium. Optional ingredients are also preferably added to the liquid electrolyte medium. Features of, and preferences for, the liquid electrolyte medium, lithium-containing salt, halogenated phosphorous flame retardant, electrochemical additive(s), and amounts of each component, are as described above.

[0099] Still another embodiment of the presently disclosed subject matter provides a process for producing an electrolyte solution for a lithium-ion battery. The process comprises combining components comprising i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated phosphorus flame- retardant. The halogenated phosphorus flame retardant is selected from a) at least one halogenated phosphate, b) at least one halogenated phosphonate, or c) a combination thereof. More particularly, a non-limiting list of exemplary halogenated phosphorus flame retardants disclosed herein includes a halogenated phosphorus flame retardant comprising at least one halogenated phosphate and / or halogenated phosphonate. In some embodiments, the electrolyte comprises a halogenated phosphorus-based flame retardant that comprises a halogenated phosphate and / or a halogenated phosphonate compound comprising at least one halogen atom (e.g., at least one Br atom) in substitution of a hydrogen atom in an alkene group of a parent nonhalogenated phosphate or phosphate compound, where the parent nonhalogenated phosphate compound is selected from the group comprising diethyl prop-2-en-l-yl phosphate, ethenyl diethyl phosphate, ethenyl diethyl phosphate, ethenyl diethyl phosphate, ethyl methyl prop-2-en-l-yl phosphate, ethenyl ethyl methylphosphate, and the parent phosphonate compound is selected from the group comprising diethyl ethenylphosphonate, dimethyl ethenylphosphonate, diethyl prop-2-en-l- ylphosphonate, dimethyl prop-2-en-l-ylphosphonate, ethyl methyl ethenylphosphonate and ethyl methyl ethenylphosphonate.

[0100] The chemical structures for these halogenated phosphate or halogenated phosphonate compounds are as follows:where w is 1, 2, or 3, and X is halogen.

[0101] In some embodiments, the halogenated phosphorus flame retardant increases the flame retardancy in the electrolyte while minimally impacting the energy storage performance, as compared to an electrolyte without any halogenated phosphorous flame retardant.

[0102] In some embodiments, the electrolyte comprises a brominated phosphorus flame retardant comprising at least one brominated phosphate or brominated phosphonate. In some embodiments, the electrolyte comprises a brominated phosphate compound selected from the group comprising 2-bromo-2-propen-l-yl diethyl phosphate, 1- bromoethenyl diethyl phosphate, 2-bromo-2-propen-l-yl dimethyl phosphate, 1- bromoethenyl dimethyl phosphate, 2-bromo-2-propen-l -yl methyl ethyl phosphate, 1 - bromoethenyl diethyl phosphate, and a halogenated phosphonate compound selected from the group consisting of diethyl (l-bromovinyl)phosphonate, dimethyl (1-bromovinyl)phosphonate, diethyl (2-bromo-2-propenyl)phosphonate, dimethyl (2- bromo-2-propenyl)phosphonate, methyl ethyl (1 -bromo vinyl)phosphonate, methyl ethyl (2-bromo-2-propenyl)phosphonate, and dimethyl [(2E')-3-bromopropy-2-en-l- yl]phosphonate. In some embodiments, the brominated phosphorous flame retardant increases the flame retardancy in the electrolyte while minimally impacting the electrochemical performance of the electrolyte, as compared to an electrolyte without any brominated phosphorous flame retardant.

[0103] The ingredients can be combined in any order, although it is preferable to add all of the components to the liquid electrolyte medium. Optional ingredients are also preferably added to the liquid electrolyte medium. Features of, and preferences for, the liquid electrolyte medium, lithium-containing salt, halogenated phosphorous flame retardant, electrochemical additive(s), and amounts of each, are as described above.

[0104] As will be appreciated by one of ordinary skill in the art, the nonaqueous electrolyte solutions of the present disclosure, which contain one or more halogenated phosphorus flame retardants, are typically used in nonaqueous electrical energy storage devices, including but limited to lithium-ion batteries comprising a positive electrode, a negative electrode, and the nonaqueous electrolyte solution. A nonaqueous electrical energy storage device, including but limited to a lithium-ion battery, can be obtained by injecting a nonaqueous electrolyte solution between the negative electrode and the positive electrode optionally having a separator therebetween.

[0105] Thus, provided herein in some embodiments is a nonaqueous electrolyte solution for a lithium-ion battery, the solution comprising i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated (e.g., brominated) phosphorus flame retardant, wherein the halogenated (e.g., brominated) phosphorus flame retardant comprises a halogenated (e.g., brominated) phosphate or halogenated (e.g., brominated) phosphonate. The halogenated phosphorus flame retardant can comprise a brominated phosphate compound selected from the group comprising 2- bromo-2-propen-l-yl diethyl phosphate, 1-bromoethenyl diethyl phosphate, 2-bromo-2- propen-l-yl dimethyl phosphate, 1-bromoethenyl dimethyl phosphate, 2-bromo-2- propen-l-yl methyl ethyl phosphate, and 1-bromoethenyl diethyl phosphate, and / or a halogenated phosphonate compound selected from the group comprising diethyl (1- bromovinyl)phosphonate, dimethyl (l-bromovinyl)phosphonate, diethyl (2-bromo-2-propenyl)phosphonate, dimethyl (2-bromo-2-propenyl)phosphonate, methyl ethyl (1- bromovinyl)phosphonate, methyl ethyl (2-bromo-2-propenyl)phosphonate, and dimethyl [(2E)-3-bromopropy-2-en-l-yl]phosphonate, or combinations thereof, e.g. two or more, three or more, four or more, etc.

[0106] The brominated phosphate or phosphonate compounds disclosed herein are further exemplified by the following chemical structures:(i.e., dimethyl [(2E)-3-bromopropy-2-en-l-yl]phosphonate).

[0107] In some preferred embodiments nonaqueous electrolyte solutions are provided where the brominated flame retardant is diethyl (l-bromovinyl)phosphonate at a concentration of about 13 wt% relative to the total weight of the nonaqueous electrolyte solution, the lithium-containing salt is lithium hexafluorophosphate (LiPFe)at a concentration of about 1.2 M, and the electrochemical additive is di(fluoro)(oxalato)borate (LiDFOB) at a concentration of about 2 wt% relative to the total weight of the nonaqueous electrolyte solution.

[0108] As shown in the Examples herein, the data demonstrates the effectiveness halogenated organophosphorus compounds as flame retardants in nonaqueous electrolyte solutions, coupled with the surprising finding that the addition of such flame retardants did not cause an appreciable decrease in performance of those nonaqueous electrolyte solutions when used in a battery. Thus, in some embodiments the halogenated flame retardant increases the flame retardancy in the nonaqueous electrolyte solution while minimally impacting the electrochemical performance of the nonaqueous electrolyte solution. For example, the flame retardancy of the nonaqueous electrolyte solution may be increased at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or more as compared to an electrical energy storage device comprising a nonaqueous electrolyte solution without the halogenated flame retardant, and yet the electrochemical performance of the nonaqueous electrolyte solution is maintained at a level at least about 70%, about 75%, about 80%, about 85%, about 90%, about 95% or about 100% of the electrochemical performance of an electrical energy storage device comprising a nonaqueous electrolyte solution without the halogenated flame retardant.

[0109] The presently disclosed subject matter provides nonaqueous electrolyte solutions for lithium-ion batteries which contain a halogenated phosphonate compound acting as a flame retardant. In the presence of the halogenated phosphonate flame - retardant(s), fires are extinguished in these nonaqueous electrolyte solutions.Examples

[0110] The following examples are included to further illustrate various embodiments of the presently disclosed subject matter. However, those of ordinary skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the presently disclosed subject matter.Example 1 - Synthesis of halogenated phosphorus-based compounds

[0111] Halogenated phosphorus-based compounds for use in electrolytes of the presently disclosed subject matter can be prepared by methods known in the art. For example, halogenated phosphorus-based compounds can be prepared from the corresponding phosphorus-based alkenes (i.e., alkene-containing phosphates or phosphonates) by contacting the phosphorus-based alkene with halogen (molecular halogen, e.g., Br2) or via a Michaelis- Arbuzov reaction, i.e., contacting a trialkyl phosphite with an alkyl halide (i.e., an alkyl halide that comprises a halogen-CHz- group and that also comprises a halogenated alkene group or an alkene group that can be halogenated). Exemplary syntheses include:Synthesis of dimethyl ( 1-bromoethenyl) phosphonate

[0112] Dichloromethane (100 mL) and dimethyl ethenylphosphonate (25 g, 0.184 mol) were added to a 250 mL round-bottom flask and stirred magnetically in an ice-cold water bath. Bromine (29.4 g, 0.184 mol) was then slowly introduced using a peristaltic pump. Once all the bromine was added, the mixture was stirred for 2 hours while allowing it to warm to room temperature. The flask was then placed back in the ice-cold water bath, and triethylamine (20.4 g, 0.20 mol) was added dropwise from a separate funnel. After the complete addition of triethylamine, the reaction was stirred for an additional 4 hours while reaching room temperature. The mixture was filtered to remove the solid that had formed, and the remaining solution was concentrated and passed through a silica gel column. The eluent was then concentrated, and the product was distilled under vacuum, yielding 11.9 g of a clear liquid.Synthesis of 2-bromoprop-2-en-l-yl diethyl phosphate

[0113] Dichloromethane (100 mL) and diethyl 2-propen-l-yl phosphate (19.4 g, 0.10 mol) were added to a 250 mL round-bottom flask and magnetically stirred in an ice-cold water bath. Bromine (16.0 g, 0.10 mol) was then slowly introduced using a peristaltic pump. After all the bromine had been added, the reaction mixture was stirred for 2 hours, allowing it to warm to room temperature. The flask was then placed back in the ice-cold water bath, and triethylamine (12.0 g, 0.12 mol) was added dropwise from an additional funnel. After the complete addition of triethylamine, the reaction was stirred for an additional 4 hours while reaching room temperature. The mixture was filtered to remove the solid that had formed, and the remaining solution was concentrated before being passed through a silica gel column. The eluent was then concentrated, and the product was distilled under vacuum, yielding 9.56 g of a clear liquid.Synthesis of diethyl (2-bromoprop-2-en-l-yl}phosphonate

[0114] A mixture of triethyl phosphite (18.7 g, 0.11 mol) and 1,2-dibromopropene (15.0 g, 0.075 mol) was added to a 100 mL round-bottom flask. The reaction was stirred under reflux with a magnetic stirrer for 4 hours. After the reaction, the mixture was distilled under vacuum, yielding 13.5 g of the product as a clear liquid.Synthesis of dimethyl [(2E)-3-bromoprop-2-en-l-yl]phosphonate

[0115] A mixture of trimethyl phosphite (13.7 g, 0.11 mol) and 1,3 -dibromopropene (15.0 g, 0.075 mol) was added to a 100 mL round-bottom flask. The reaction was stirred under reflux with a magnetic stirrer for 4 hours. After the reaction, the mixture was distilled under vacuum, yielding 11.3 g of the product as a clear liquid.Example 2- Flame retardancy (UL-94) testing

[0116] A modified horizontal UL-94 test was performed. This modified horizontal UL- 94 test is quite similar to known, published horizontal UL-94 tests. See in this regard, e.g., Otsuki, M. et al. "Flame-Retardant Additives for Lithium-Ion Batteries." Lithium- Ion Batteries. Ed. M. Yoshio et al. New York, Springer, 2009, 275-289. The modified UL-94 test was as follows: wicks were cut from round fiberglass wick, and cut edges were made smooth, and then dust and particles were removed from the wick surface. The wicks were dried for 20 hours at 120°C prior to testing. Wicks were 5 + 0.1 inch (1 2.7 + 0.2.5 cm) long.

[0117] Each specimen to be tested was prepared in a dry box in a 4 oz. (120 mL) glass jar, by combining the desired amount of flame retardant and, when present, electrochemical additive, with the desired amount of the plain electrolyte solution, e.g., 15 wt% of the halogenated phosphorus flame retardant and 85 wt% of the plain electrolyte solution, were combined to form the electrolyte solution containing the flame retardant. Prior to combination with the flame retardant, the plain electrolyte solution contained 1.2 M LiPFg in ethylene carbonate / ethyl methyl carbonate (wt ratio 3:7). Each wick was soaked in the electrolyte solution for 30 minutes.

[0118] Each specimen was removed from the electrolyte solution and held over the electrolyte solution until no dripping occurred, and then placed in a 4 oz. (120 mL) glass jar: the cap was closed to prevent electrolyte solution from evaporating.

[0119] The burner was ignited and adjusted to produce a blue flame 20 ± 1 mm high.

[0120] A specimen was removed from its 4 oz. (120 mL) glass jar, and the specimen was placed on a metal support fixture in a horizontal position, secured at one end of the wick.

[0121] If an exhaust fan was running, it was shut off for the test.

[0122] The flame was at an angle of 45 ± 2 degrees to the horizontal wick. One way to accomplish this when the burner had a burner tube was to incline the central axis of the burner tube toward an end of the specimen at an angle of 45 ± 2 degrees from the horizontal.

[0123] The flame was applied to the free end of the specimen for 30 ± 1 seconds without changing its position; the burner was removed after 30 ± 1 seconds, or as soon as the combustion front on the specimen reached the 1 inch (2.54 cm) mark. If the specimen continued to burn after removal of the test flame, the time in seconds was recorded, for either the flame to extinguish or for the combustion front (flame) to travel from the 1 inch (2.54 cm) mark to the 4 inch (10.16 cm) mark.

[0124] A specimen was considered to be "not flammable" if the flame extinguished when the burner was removed. A specimen was considered to be "flame retardant" if the flame extinguished before reaching the 1 inch (2.54 cm) mark. A specimen was considered to be "self-extinguishing" if the flame went out before reaching the 4 inch (10.16 cm) mark.

[0125] Results of the UL-94 flame retardancy testing of the disclosed halogenated phosphate and phosphonate flame retardants are summarized in Table 1. See also Figures 1 A and IB which compare results of testing of an electrolyte solution without a flame retardant additive (Figure 1A) and an electrolyte with 13 wt% diethyl (1- bromovinyl)phosphonate (Figure IB).

[0126] Table 1. UL-94 Testing Result Flame Retardant

[0127] As the results show, the brominated phosphate and phosphonate flame retardants of the presently disclosure provided effective flame retardancy sufficient to be considered a flame retardant for use in batteries.Example 3- Flammability testing

[0128] Electrolyte flammability testing employs a more rigorous standard that attempts to closely approximate the conditions under which electrolytes in abuse conditions will need to exhibit non-flammable or flame retardant properties, namely a venting cell with an ignition source. To realize this end, the test configuration for flammability testing involves filling an 18650-sized can, commonly used in commercial batteries, with approximately 5mL of electrolyte, crimping the cell with a typical cell header assembly,and heating the electrolyte-only cell at a fixed rate of 5 °C / min with a spark- wire ignition source at a fixed position roughly 2 inches above the cell header. Upon cell venting, which usually occurs near 200°C, the hot electrolyte becomes aerosolized and is exposed to the spark-wire ignition source where it is monitored for ignition. This thermal ramp testing was conducted to evaluate the flammability of the disclosed nonaqueous electrolyte solutions containing brominated flame retardants. The testing included evaluating the disclosed compounds when vaporized in presence of ignition source. More specifically, temperature measurements were taken from a series of temperature probes in and above empty 18650 cans filled with 5 ml of electrolyte solution with or without the disclosed halogenated phosphorus flame retardants.

[0129] Exemplary results are shown in Figs. 2A and 2B. More particularly, FIG. 2A shows the flammability measurements of a nonaqueous electrolyte solution comprising 10% Hishicolin-O. At about 40 min a noticeable temperature spike is apparent in Fig. 2A, which correlates to an observed flame and external combustion of the electrolyte solution. In marked contrast, when the electrolyte solution contained one of the disclosed brominated flame retardants no such temperature spike (FIG. 2B) or flame was observed. The data from these tests confirmed the effective flame retardance of the disclosed brominated flame retardants when incorporated in a nonaqueous electrolyte solution.Example 4- Coin cell testing

[0130] Tests of some nonaqueous electrolyte solutions containing brominated flame retardants in coin cells were also carried out. For the studies described in herein, exemplary coin cells with an areal capacity of roughly 2 mAh / cm2were assembled using nonaqueous electrolyte solutions containing the desired amount of flame retardant (described as a wt% relative to the total weight of the nonaqueous electrolyte solution) as disclosed herein. The coin cells were then subjected to electrochemical cycling of CCCV charging to 4.2 V at C / 5, with a current cutoff of C / 50 in the CV portion, and CC discharge at C / 5 to 3.0 V.

[0131] Coin cell testing was evaluated for each of a) an electrolyte solution with 8 wt% diethyl 2-bromoethylphosphonate (comparative; as shown in Fig. 3); b) an electrolyte solution with 8 wt% 2-bromo-2-propen-l-yl diethyl phosphate; c) an electrolyte solution with 15 wt% diethyl (l-bromovinyl)phosphonate + 2 wt% LiDFOB. Results ofCoulombic Efficiency measurements up to 10 cycles are shown in Figure 4. The findings reveal an unexpected result: the brominated alkene phosphate or phosphonate exhibits significantly higher coulombic efficiency compared to the brominated alkyl phosphonate.

[0132] Long term 18650 cycling was evaluated for each of a) a standard electrolyte used in lithium-ion batteries with no flame retardant (control; Gen2); b) an electrolyte solution with 13 wt% diethyl (l-bromovinyl)phosphonate + 2% LiDFOB, and c) a second control (same as control / Gen2) plus 2 wt% LiDFOB. Results of Coulombic Efficiency measurements up to 501 cycles are shown in Table 2.

[0133] Table 2.

[0134] Further comparative 18650 cycling testing was conducted, including a standard electrolyte used in lithium-ion batteries with no flame retardant (comparative example 1 ; control). This was compared to an electrolyte solution with 13 wt% diethyl (1- bromovinyl)phosphonate + 2 wt% LiDFOB. Finally, a second comparative example included the control electrolyte (same as comparative example 1) plus 2 wt% LiDFOB to confirm that the results observed with the diethyl (l-bromovinyl)phosphonate test sample was not due to the addition of LiDFOB. Comparative coulombic efficiencieswere measured and recorded over increasing numbers of cycles up to 701 cycles. Results are summarized in Table 3 below.

[0135] Table 3.

[0136] As the data in Table 3 shows, while the Coulombic efficiency of comparative example 1 (control) steadily decreased as the number of cycles increased (83% at 101 cycles, down to 68% at 501 cycles), the efficiency observed with the electrolyte solution having the flame retardant (diethyl (l-bromovinyl)phosphonate + 2 wt% LiDFOB) surprisingly maintained a high level of efficiency even at 701 cycles.

[0137] Additional Coulombic efficiency studies were conducted in coin cells as described above out to 50 cycles using electrolytes comprising the following halogenated phosphorus additives (13 wt%) and LiDFOB (2 wt%):(dimethyl (l-bromoethenyl)phosphonate, also known as dimethyl 1- bromovinyl)phosphonate) ;O(2-bromoprop-2-en-l-yl diethyl phosphate, also known as (2-bromo- propen-l-yl) diethyl phosphate);(diethyl (2-bromoprop-2-en-l-yl)phosphonate, also known as diethyl (2- bromo-2-propenyl)phosphonate); and(dimethyl [(2E)-3-bromoprop-2-en-l-yl]phosphonate). Results are shown in Table 4 below.Table 4.Summary and Conclusions from Examples 1-4

[0138] The data in the Examples illustrates the effectiveness of the disclosed halogenated phosphonates as flame retardants in nonaqueous electrolyte solutions,coupled with the surprising finding that the addition of such flame retardants did not cause an appreciable decrease in performance of those nonaqueous electrolyte solutions when used in a battery. Moreover, indeed, in some aspects, the addition of the disclosed halogenated phosphates or halogenated phosphonates appears to have maintained and / or increased the level of performance over time as compared to nonaqueous electrolyte solutions without the halogenated phosphonates. Without being bound by any particular theory or mechanism of action, this unexpected finding of flame retardancy coupled with maintenance of performance or stability in an electrical energy storage device is believed to be attributable to the compatibility of the halogen alkene bond or bonds within the same molecule of an organophosphorus compound within the nonaqueous electrolyte solutions, which has not been the case in prior flame retardants, including those with compounds comprising an organophosphorus moiety and an alkyl (sp3) moiety.

[0139] It will be understood that various details of the presently disclosed subject matter may be changed without departing from the scope of the presently disclosed subject matter. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.

Claims

CLAIMSWhat is claimed is:

1. An electrical energy storage device electrolyte comprising: a) an aprotic organic solvent system; b) an alkali metal salt; and c) at least one or more halogenated phosphorus-based compounds in an amount of 0.01 wt% to 60 wt% of the electrolyte, wherein each of the one or more halogenated phosphorus-based compounds has a structure of Formula (I) or Formula (IV):ormu a , wherein, n is 1 , 2, 3, 4, or 5; w is 0 or 1 ; x and y are each 0, 1, or 2, and z is 1, 2, or 3, wherein the sum of x, y, and z is 3;A is oxygen or sulfur;Z is oxygen, sulfur, or aliphatic carbon;L is oxygen, sulfur, or aliphatic carbon;Ri is an aliphatic or aliphatic ether group having 1-5 carbons;R2 is an aliphatic or aliphatic ether group having 1-5 carbons; andR3 is an aliphatic group having 2-5 carbons, wherein said aliphatic group comprises at least one halogenated alkene group.

2. The electrolyte of claim 1, wherein the aprotic organic solvent comprises a solvent selected from the group consisting of an open-chain or cyclic carbonate, a carboxylic acid ester, a nitrile, an ether, a sulfone, a ketone, a lactone, a dioxolane, a glyme, a crown ether, a siloxane, a phosphoric acid ester, a phosphite, a mono- or polyphosphazene, and mixtures thereof.

3. The electrolyte of claim 1, wherein the cation of the alkali metal salt comprises lithium, sodium, aluminum, or magnesium.

4. The electrolyte of claim 1, wherein the electrolyte further comprises an additive.

5. The electrolyte of claim 4, wherein the additive is selected from the group consisting of a sulfur-containing compound, a phosphorus-containing compound, a boron-containing compound, a silicon-containing compound, a fluorine-containing compound, a nitrogen containing compound, a compound containing at least one unsaturated carbon-carbon bond, a carboxylic acid anhydride, and mixtures thereof.

6. The electrolyte of claim 1, wherein the additive is present at a concentration of about 0.01 wt% to about 5 wt% of the electrolyte.

7. The electrolyte of claim 1 , wherein the electrolyte further comprises an ionic liquid.

8. The electrolyte of claim 7, wherein the ionic liquid comprises an organic cation selected from the group consisting of a N-alkyl-N-alkyl-pyrrolidinium, a N-alkyl-N- alkyl-pyridnium, a N-alkyl-N-alkyl-sulfonium, a N-alkyl-N-alkylammonium, and a N- alkyl-N-alkylpiperdinium.

9. The electrolyte of claim 7, wherein the ionic liquid comprises an anion selected from the group consisting of tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, and trifluoroacetate.

10. An electrical energy storage device comprising: a cathode; an anode; and an electrolyte according to claim 1.

11. The device of claim 10, wherein the cathode comprises a lithium metal oxide, spinel, olivine, carbon-coated olivine, LiFePCh, LiCoC , LiNiCh, LiNi ilCovMet:O2, LiMno 5Nio 5O2, LiMno 3Coo 3Nio 3O2, LiMn2O4, LiFeO2, Lii+C’Nic<MnpCoYMet'5O2-z’ , Fz>,Aft B2(XO4)3 (NASICON), vanadium oxide, lithium peroxide, sulfur, polysulfide, a lithium carbon mono fluoride or a mixture of any two or more thereof, where Met is selected from the group consisting of Al, Mg, Ti, B, Ga, Si, Mn and Co; Met’ is selected from the group consisting of Mg, Zn, Al, Ga, B, Zr or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu or Zn; B is Ti, V, Cr, Fe and Zr; X is P, S, Si, W or Mo; and wherein 0<x<0.3, 0<y<0.5, 0<z<0.5, 0<x'<0.4, 0<a<l, O<P<1, 0<y<l, 0<S<0.4, 0<z'<0.4 and 0<h'<3.

12. The device of claim 10, wherein the anode comprises lithium metal, graphitic material, amorphous carbon, Li^isOiz, tin alloy, silicon alloy, intermetallic compound or a mixture thereof.

13. The device of claim 10, wherein the device is selected from the group consisting of a lithium battery, a lithium-ion battery, a lithium-sulfur battery, a lithium-air battery, a sodium ion battery, a magnesium battery, an electrochemical cell, a capacitor, a lithium / MnOz battery, a Li / poly(carbon monofluoride) battery, and a solar cell.

14. The device of claim 10, wherein the device further comprises a porous separator separating the anode and cathode from each other.

15. The device of claim 14, wherein the porous separator comprises an electron beam- treated micro-porous polyolefin separator or a microporous polymer film comprising a polymer selected from the group consisting of nylon, cellulose, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, polybutene, and a co-polymer or blend thereof.

16. The device of claim 10, wherein the aprotic organic solvent comprises a solvent selected from the group consisting of an open-chain or cyclic carbonate, a carboxylic acid ester, a nitrile, an ether, a sulfone, a ketone, a lactone, a dioxolane, a glyme, a crown ether, a siloxane, a phosphoric acid ester, a phosphite, a mono- or polyphosphazene, and a mixture thereof.

17. The device of claim 10, wherein the cation of the alkali metal salt comprises lithium, sodium, aluminum or magnesium.

18. The device of claim 10, wherein the electrolyte further comprises an additive.

19. The device of claim 18, wherein the additive is selected from the group consisting of a sulfur-containing compound, a phosphorus-containing compound, a boron- containing compound, a silicon-containing compound, a fhiorine-containing compound,a nitrogen containing compound, a compound containing at least one unsaturated carboncarbon bond, a carboxylic acid anhydride, and a mixture thereof.

20. The device of claim 10, wherein the electrolyte further comprises an ionic liquid.

21. The device of claim 20, wherein the ionic liquid comprises an organic cation selected from the group consisting of a N-alkyl-N-alkyl-pyrrolidinium, a N-alkyl-N- alkyl-pyridnium, a N-alkyl-N-alkyl-sulfonium, a N-alkyl-N-alkyl-ammonium, and a N- alky 1-N- alky 1-piperdinium.

22. The device of claim 20, wherein the ionic liquid comprises an anion selected from the group consisting of tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl) imide, and trifluoroacetate.

23. A flame retarded nonaqueous electrolyte solution composition for a lithium-ion battery, the solution comprising i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated phosphorus -based flame retardant having a structure of Formulas (II) or (III).OR.5O ' R ,RA'Formula (II),Formula (III), where Ri, R2 and R3 are each selected from the group consisting of saturated alkyl, alkene or a halogenated alkene group having 1 to 5 carbon atoms, and wherein at least one of Ri, R2 and R3 is a halogenated alkene group.

24. The nonaqueous electrolyte solution of claim 23, wherein the halogenated phosphorus-based flame retardant comprises a halogenated phosphate compoundselected from the group consisting of 2-bromo-2-propen-l-yl diethyl phosphate, 1- bromoethenyl diethyl phosphate, 2-bromo-2-propen-l-yl dimethyl phosphate, 1- bromoethenyl dimethyl phosphate, 2-bromo-2-propen-l-yl methyl ethyl phosphate, 1- bromoethenyl diethyl phosphate, and a halogenated phosphonate compound selected from the group consisting of diethyl (l-bromovinyl)phosphonate, dimethyl (1- bromovinyl)phosphonate, diethyl (2-bromo-2-propenyl)phosphonate, dimethyl (2- bromo-2-propenyl)phosphonate, methyl ethyl (l-bromovinyl)phosphonate, methyl ethyl (2-bromo-2-propenyl)phosphonate, and dimethyl [(2E)-3-bromopropy-2-en-l- yl]phosphonate.

25. The nonaqueous electrolyte solution of claim 23 or claim 24, wherein the liquid electrolyte medium is selected from the group consisting of ethylene carbonate (1,3- dioxolan-2-one), dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dioxolane, dimethoxy ethane (glyme), tetrahydrofuran, methanesulfonyl chloride, ethylene sulfite, 1,3-propylene glycol boric ester, and combinations thereof.

26. The nonaqueous electrolyte solution of any of claims 23 to 25, wherein the lithium- containing salt is selected from the group consisting of lithium chloride, lithium bromide, lithium iodide, lithium perchlorate, lithium nitrate, lithium thiocyanate, lithium aluminate, lithium tetrachloro aluminate, lithium tetrafluoroaluminate, lithium tetraphenylborate, lithium tetrafluoroborate, lithium bis(oxalato)borate (LiBOB), lithium di(fluoro)(oxalato)borate (LiDFOB), lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium titanium oxide, lithium manganese oxide, lithium cobalt oxide (LiCoCh), lithium nickel oxide (LiNiCh), lithium alkyl carbonates in which the alkyl group has 1 to 6 carbon atoms, lithium methyl sulfonate, lithium trifluoromethyl sulfonate, lithium pentafluoroethyl sulfonate, lithium pentafluorophenylsulfonate, lithium fluorosulfonate, lithium bis(trifluoromethy 1 sulfony 1 )imide, lithium bis(pentafluoroethy 1 sulfo ny 1 )imide, lithium (ethylsulfonyl)(trifluoromethylsulfonyl)imide and combinations thereof, optionally wherein the halogenated phosphorus flame retardant is diethyl (1- bromovinyl)phosphonate (DBVP) at a concentration of about 13 wt%, and the lithium- containing salt is lithium di(fluoro)(oxalato)borate (LiDFOB) at a concentration of about 2 wt%.

27. The nonaqueous electrolyte solution of any of claims 23 to 26, further comprising at least one electrochemical additive selected from: a) unsaturated cyclic carbonates containing three to about six carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about five carbon atoms and one to about four fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about nine carbon atoms, d) trihydrocarbyl phosphates containing three to about twelve carbon atoms, e) cyclic sultones containing three to about eight carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5 -membered or 6-membered ring and containing two to about six carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered or 6-membered ring and containing two to about six carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered, 7-membered, or 8- membered ring and containing two to about six carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing.

28. The nonaqueous electrolyte solution of any of claims 23 to 27, wherein the halogenated phosphorus-based flame retardant increases the flame retardancy in the nonaqueous electrolyte solution while minimally impacting the electrochemical performance of the nonaqueous electrolyte solution, optionally wherein the flame retardancy of the nonaqueous electrolyte solution is increased at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or more as compared to a nonaqueous electrolyte solution without the halogenated phosphorus flame retardant, optionally wherein the electrochemical performance of the nonaqueous electrolyte solution is maintained at a level at least about 70%, about 75%, about 80%, about 85%, about 90%, about 95% or about 100% of the electrochemical performance of a nonaqueous electrolyte solution without the halogenated phosphorus- based flame retardant.

29. The nonaqueous electrolyte solution of any of claims 23 to 28, wherein the halogenated phosphorus -based flame retardant is included in the nonaqueous electrolyte solution in a flame retardant amount, optionally wherein the halogenated phosphorus- based flame retardant is included at about 8 wt% to about 15 wt% flame retardant molecules relative to the total weight of the nonaqueous electrolyte solution, optionally in a range of about 10 wt% to about 13 wt% flame retardant molecules relative to the total weight of the nonaqueous electrolyte solution.

30. A nonaqueous lithium-ion battery comprising a positive electrode, a negative electrode, and the nonaqueous electrolyte solution of any one of claims 23 to 29.

31. Use of the nonaqueous electrolyte solution of any one of claims 23 to 29 in a lithium-ion battery.

32. A process for producing a nonaqueous electrolyte solution for a lithium-ion battery, which process comprises combining components comprising: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one halogenated phosphorus-based flame retardant having a structure of Formula (II) or Formula (III) of claim 23.

33. The process of claim 32, wherein the halogenated phosphorus-based flame retardant comprises a halogenated phosphate compound selected from the group consisting of 2-bromo-2-propen-l-yl diethyl phosphate, 1-bromoethenyl diethyl phosphate, 2-bromo-2-propen-l-yl dimethyl phosphate, 1-bromoethenyl dimethyl phosphate, 2-bromo-2-propen-l-yl methyl ethyl phosphate, 1-bromoethenyl diethyl phosphate, and / or a halogenated phosphonate compound selected from the group consisting of diethyl (l-bromovinyl)phosphonate, dimethyl (l-bromovinyl)phosphonate, diethyl (2-bromo-2-propenyl)phosphonate, dimethyl (2-bromo-2- propenyl)phosphonate, methyl ethyl (l-bromovinyl)phosphonate, methyl ethyl (2- bromo-2-propenyl)phosphonate, and dimethyl [(2E)-3-hromopropy-2-en-l - yl]phosphonate.

34. The process of any of claims 32 to 33, wherein the halogenated phosphorus-based flame retardant comprises a combination of two or more halogenated phosphate compounds selected from the group consisting of 2-bromo-2-propen-l-yl diethyl phosphate, 1-bromoethenyl diethyl phosphate, 2-bromo-2-propen-l-yl dimethyl phosphate, 1-bromoethenyl dimethyl phosphate, 2-bromo-2-propen-l-yl methyl ethyl phosphate, 1-bromoethenyl diethyl phosphate, and / or a combination of two or more halogenated phosphonate compounds selected from the group consisting of diethyl (1- bromovinyl)phosphonate, dimethyl (l-bromovinyl)phosphonate, diethyl (2-bromo-2- propenyl)phosphonate, dimethyl (2-bromo-2-propenyl)phosphonate, methyl ethyl (1- bromovinyl)phosphonate, methyl ethyl (2-bromo-2-propenyl)phosphonate, and dimethyl [(2E)-3-bromopropy-2-en-l-yl]phosphonate.

35. The process of any of claims 32 to 34, wherein the liquid electrolyte medium is selected from the group consisting of ethylene carbonate (l,3-dioxolan-2-one), dimethylcarbonate, ethyl methyl carbonate, diethyl carbonate, dioxolane, dimethoxy ethane (glyme), tetrahydrofuran, methanesulfonyl chloride, ethylene sulfite, 1,3-propylene glycol boric ester, and combinations thereof.

36. The process of any of claims 32 to 35, wherein the lithium-containing salt is selected from the group consisting of lithium chloride, lithium bromide, lithium iodide, lithium perchlorate, lithium nitrate, lithium thiocyanate, lithium aluminate, lithium tetrachloroaluminate, lithium tetrafluoroaluminate, lithium tetraphenylborate, lithium bis(oxalato)borate, lithium di(fluoro)(oxalato)borate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium titanium oxide, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium alkyl carbonates (with alkyl groups containing 1 to 6 carbon atoms), lithium methyl sulfonate, lithium trifluoromethyl sulfonate, lithium pentafluoroethyl sulfonate, lithium pentafluorophenylsulfonate, lithium fluorosulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium (ethylsulfonyl)(trifhioromethyl sulfonyl)imide, lithium borohydride, lithium hexafluoroacetylacetonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)amide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorosilicate, lithium hexafluorotitanate, lithium hexafluorostannate, lithium hexafluoroaluminate, lithium hexafluorozirconate, lithium difluorophosphate, lithium fluoroborate, lithium trifluoromethanesulfonate, lithium fluoride, and combinations thereof.

37. The process of any of claims 32 to 36, further comprising adding at least one electrochemical additive selected from: a) unsaturated cyclic carbonates containing three to about six carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about five carbon atoms and one to about four fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about nine carbon atoms, d) trihydrocarbyl phosphates containing three to about twelve carbon atoms, e) cyclic sultones containing three to about eight carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered or 6-membered ring and containing two to about six carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered or 6-membered ring and containing two to about six carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered, 7-membered, or 8- membered ring and containingtwo to about six carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing.

38. The process of any of claims 32 to 37, wherein the halogenated phosphorus-based flame retardant is included in the nonaqueous electrolyte solution in a flame retardant amount, optionally wherein the halogenated phosphorus-based flame retardant is included at about 8 wt% to about 15 wt% flame retardant molecules relative to the total weight of the nonaqueous electrolyte solution, optionally in a range of about 10 wt% to about 13 wt% flame retardant molecules relative to the total weight of the nonaqueous electrolyte solution.