Brominated sulfite flame retardant additives for energy storage devices

Abstract

A nonaqueous electrolyte solution for an energy storage device, the solution comprises i) an aprotic organic solvent system; ii) an alkali metal salt; and iii) at least one brominated sulfite-based flame-retardant additive compound. The halogenated sulfite flame retardant increases the flame retardancy and / or thermal runaway inhibitory capacity 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 and energy storage devices containing the same are provided. Electrical energy storage devices with these enhanced properties, including enhanced flame retardancy and thermal runaway inhibitory capacity, are also provided.

Description

[0001] Attorney Docket No. 1710.00044WO BROMINATED SULFITE FLAME RETARDANT ADDITIVES FOR ENERGY STORAGE DEVICES CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 678,732, filed August 2, 2024, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure relates generally to flame retardants and thermal runaway inhibitors for an electrical energy storage device, and more particularly to such a device comprising a brominated sulfite electrolyte additive that chemically interferes with flame propagation. BACKGROUND 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 flame retardants 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. 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, and inhibition of thermal runaway events, with minimal impact on device performance at a reasonable cost. BRIEF SUMMARY 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 Attorney Docket No. 1710.00044WO 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. Provided in some embodiments are electrical energy storage devices comprising a cathode, an anode, and an electrolyte, the electrolyte comprising: an aprotic organic solvent system; an alkali metal salt; and an electrolyte additive that chemically interferes with flame propagation, the electrolyte additive represented by formula (I) or formula formula (II), wherein R1, R2, R3, and atom, a C1-C5 bromoalkyl group, or a C2-C5 bromoalkene group, and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2-C5 bromoalkene group comprising at least one bromine atom. In some embodiments, two or more of R1, R2, R3, and R4 are a C1-C5 bromoalkyl group comprising at least one bromine atom and / or a C2-C5 bromoalkene group comprising at least one bromine atom. In some embodiments, the electrolyte additive that chemically interferes with flame propagation is fire damping, flame retarding, and / or thermal runaway inhibiting. In some embodiments, the electrolyte additive that chemically interferes with flame propagation is a radical scavenger. In some embodiments, the aprotic organic solvent comprises an open-chain or cyclic carbonate, carboxylic acid ester, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono- or polyphosphazene or mixtures thereof. In some embodiments, the additive comprises a concentration in the electrolyte of from about 0.01 wt. % to about 50wt. %. In some embodiments, the electrolyte further comprises an ionic liquid. In some embodiments, the ionic liquid comprises an organic cation comprising N-alkyl-N- alkylpyrrolidinium, N-alkyl-N-alkyl-pyridnium, N-alkyl-Nalkyl-sulfonium, N-alkyl-N- alkyl-ammonium, or N-alkylN-alkyl-piperdinium. In some embodiments, the ionic liquid Attorney Docket No. 1710.00044WO comprises an anion comprising tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, or trifluoroacetate. In some embodiments, the cathode comprises a lithium metal oxide, spinel, olivine, carbon-coated olivine, LiFePO4, LiCoO2, LiNiO2, LiNi1xCoyMetzO2, LiMn0.5Ni0.5O2 , LiMn0.3Co0.3Ni0.3O2, LiMn2O4 , LiFeO2 , Li1+x’NiaMnbCogMet'dO2-z’ ,Fz’, Ah’B2(XO4)3 (NASICON), vanadium oxide, lithium peroxide, 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. In some embodiments, the anode comprises lithium metal, graphitic material, amorphous carbon, Li4Ti5O12, tin alloy, silicon alloy, intermetallic compound or mixtures thereof. In some embodiments, the device comprises a lithium battery, lithium-ion battery, lithium-sulfur battery, lithium-air battery, sodium ion battery, magnesium battery, electrochemical cell, capacitor, lithium / MnO2 battery, Li / poly(carbon monofluoride) battery, or solar cell. In some embodiments, the device further comprises a porous separator separating the anode and cathode from each other. In some embodiments, the porous separator comprises an electron beam-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. In some embodiments, the aprotic organic solvent comprises an open-chain or cyclic carbonate, carboxylic acid ester, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono- or polyphosphazene or mixtures thereof. In some embodiments, the alkali metal salt comprises a cation selected from the group consisting of lithium, sodium, aluminum and magnesium. In some embodiments, the electrolyte additive decreases flame propagation in the device while minimally impacting the electrochemical performance of the device. In some embodiments, the decrease in flame propagation is 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 without the electrolyte additive. In some embodiments, the electrolyte additive increases inhibition of thermal runaway and / or flame retardancy of the device, wherein the increase is at Attorney Docket No. 1710.00044WO 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 without the electrolyte additive. In some embodiments, the electrochemical performance of the device is maintained at a level of at least about 70%, about 75%, about 80%, about 85%, about 90%, about 95% or about 100% of the electrochemical performance of a device without the electrolyte additive. Also provided herein are electrical energy storage systems comprising a first electrical energy storage device and a second electrical energy storage device, wherein the second electrical energy storage device is operatively connected to the first electrical energy storage device. Also provided are processes for producing an electrical energy storage device with increased flame retardancy and / or increased thermal runaway inhibition, which processes comprise combining components comprising: i) a cathode; ii) an anode; iii) and an electrolyte, the electrolyte comprising: an aprotic organic solvent system; an alkali metal salt; and an electrolyte additive that chemically interferes with flame propagation, the electrolyte additive represented by formula (I) or formula (II): , wherein R1, R2, R3, and R4 are C5 bromoalkyl group, or a C2-C5 bromoalkene group, and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2-C5 bromoalkene group comprising at least one bromine atom. In some embodiments, the electrolyte additive that chemically interferes with flame propagation is fire damping, flame retarding, and / or thermal runaway inhibiting. In some embodiments, the additive comprises a concentration in the electrolyte of from about 0.01 wt. % to about 50wt. %. In some embodiments, the electrolyte additive decreases flame propagation in the device while minimally impacting the electrochemical performance of the device. In some embodiments, the decrease in flame propagation and / or flammability is at least about 25%, 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 Attorney Docket No. 1710.00044WO energy storage device without the electrolyte additive. In some embodiments, the electrolyte additive increases inhibition of thermal runaway and / or flame retardancy of the device, wherein the increase is 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 without the electrolyte additive. Also provided herein are flame retardant compounds, the flame retardant compounds comprising 4-(2-bromoethenyl)-1,3,2-dioxathiolane 2-oxide. In some embodiments, the flame retardant compound increases inhibition of thermal runaway and / or flame retardancy in an environment, wherein the increase is 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 environment without the flame retardant compound, optionally wherein the environment is an electrical energy storage device. Also provided herein are methods of making the flame retardant compound as disclosed herein, the methods comprising: mixing 4-ethenyl-1,3,2-dioxathiolane 2-oxide and dichloromethane to form a first mixture; adding bromine to the first mixture to form a second mixture; adding triethylamine to the second mixture to form a third mixture; and distilling the third mixture to yield 4-(2-bromoethenyl)-1,3,2-dioxathiolane 2-oxide. In some embodiments, distilling the third mixture comprises removing solvent from the third mixture via rotary evaporator, and passing a residual solution through a silica gel column under vacuum. 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. DETAILED DESCRIPTION I. Definitions 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. 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. Attorney Docket No. 1710.00044WO 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. 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 was first 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. 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. 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 Attorney Docket No. 1710.00044WO understanding that such combinations are entirely within the scope of the invention and the claims. 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. 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. 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. 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. 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. 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. Attorney Docket No. 1710.00044WO 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. 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. The term "thermal runaway inhibitor" or "TRI" as used herein refers to a class of compounds that suppresses exothermic reactions that occur at high temperatures in the electrolyte mixture of an electrical energy storage device and / or electrochemical cell by way of: chemical interference with flame propagation via free radical scavenging and / or fire damping, production of incombustible gases that dilute the available air supply, absorption of heat by endothermic decomposition or change of state, formation of impervious fire-resistant coatings, an unknown mechanism or any combination thereof. Therefore, TRI improves flame-retarding properties of the electrolytes by reducing the risk of fire or explosion caused by thermal runaway. Additionally, TRI is used to describe the exemplary compounds identified herein, as well as their equivalents. The term "flame-retarding" indicates a reduction or elimination of the tendency of a combustible material to burn. Thus, a flame-retarding electrolyte composition is one in which the basic flammability has been reduced, including for example by measuring accelerated rate calorimetry. Further, the phrase "flame-retarding additive" or "flame- retarding electrolyte" is used to describe an additive or electrolyte comprising a flame- retarding compound or a TRI. In some embodiments, “sulfite” can be synonymous with dioxathiolane or any other nomenclature representing (SO)O2. II. Brominated Sulfite Flame Retardants for Electrical Energy Storage Devices The presently disclosed subject matter provides electrolyte for an energy storage device which contains a halogenated and / or brominated sulfite flame-retardant additive and / or thermal runaway inhibitor (TRI) whose molecular structure is comprised of at least one halogen, e.g. bromine, atom and one sulfite group. In particular the flame- retardant additive and / or TRI can be comprised of a brominated sulfite. While not Attorney Docket No. 1710.00044WO wanting to be limited to any single theory, the presence of the flame-retardant additives and / or TRIs of this invention 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, and / or thermal runaway events, which can also be mitigated by the presence of the flame-retardant additive and / or TRI of this invention. Surprisingly, addition of the presently disclosed flame-retardant additives and / or TRIs can provide acceptable electrical storage performance of the electrical devices provided by this invention. A brominated sulfite of this invention was evaluated as a flame retardant and / or TRI in various electrolyte blends which may find use in energy storage devices. Although not wishing to be bound by any particular theory or mechanism of action, it is believed that there is a synergy between bromine and sulfite. For example, with an amount of sulfur present, as discussed herein, less bromine is needed for an effective system than if it were to be an all-bromine flame retardant and / or TRI. 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. Throughout this document, the term “halogenated sulfite flame retardant” is used interchangeably with “halogenated sulfite additive”, “brominated sulfite additive” “halogenated sulfite compound”, “brominated sulfite compound”, “halogenated flame retardant”, or “brominated flame retardant.” Thermal runaway is the condition where the rate of heat generation within an energy storage device or battery exceeds the device’s or battery's (and its operating environment's) capacity to dissipate the heat. This condition can cause accelerated dryout and increased charging current acceptance, which will eventually result in the battery igniting and / or exploding. In consumer-oriented lithium-ion batteries, manufacturers employ external safety devices to minimize these potential hazards. Attorney Docket No. 1710.00044WO 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 The term "thermal runaway inhibitor" or "TRI" as used herein refers to a class of compounds that suppresses exothermic reactions that occur at high temperatures in the electrolyte mixture of an electrical energy storage device and / or electrochemical cell by way of: chemical interference with flame propagation via free radical scavenging and / or fire damping, production of incombustible gases that dilute the available air supply, absorption of heat by endothermic decomposition or change of state, formation of impervious fire-resistant coatings, an unknown mechanism or any combination thereof. Therefore, TRI improves flame-retarding properties of the electrolytes by reducing the risk of fire or explosion caused by thermal runaway. Additionally, TRI is used to describe the exemplary compounds identified herein, as well as their equivalents. The term "flame-retarding" indicates a reduction or elimination of the tendency of a combustible material to burn. Thus, a flame-retarding electrolyte composition is one in which the basic flammability has been reduced, including for example by measuring accelerated rate calorimetry. Further, the phrase "flame-retarding additive" or "flame- retarding electrolyte" is used to describe an additive or electrolyte comprising a flame- retarding compound or a TRI. 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, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono-, oligo-, or polyphosphazene or mixtures thereof. In some embodiments, preferred solvents include ethylene carbonate (l,3- dioxolan-2-one), dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, Attorney Docket No. 1710.00044WO 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. 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 (LiCoO2), lithium nickel oxide (LiNiO2), lithium alkyl carbonates in which the alkyl group has 1 to 6 carbon atoms, lithium methy1sulfonate, lithium trifluoromethy1sulfonate, lithium pentafluoroethy1sulfonate, lithium pentafluorophenylsulfonate, lithium fluorosulfonate, lithium bis(trifluoromethy1sulfony1)imide, lithium bis(pentafluoroethy1sulfony1)imide, lithium (ethylsulfonyl)(trifluoromethylsulfonyl)imide, and mixtures of any two or more of the foregoing. 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. 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 or TRI 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 alkaline earth metal salts, e.g., magnesium salts, calcium salts, antimony salts, strontium salts, Attorney Docket No. 1710.00044WO and barium salts. In some aspects, the salts in the non-aqueous electrolyte solution are only one or more lithium salts. 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. 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. In an embodiment of the presently disclosed subject matter, the flame retardant 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. 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 some embodiments 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 Attorney Docket No. 1710.00044WO 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 this invention it is preferred that the halogenated sulfite 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. In one embodiment of the practice of the presently disclosed subject matter, the concentration of brominated sulfite flame retardants combined with electrolyte generally have a bromine content of 4– 20% of the total electrolyte composition. In another embodiment, about 6 wt% or more of the total electrolyte, preferably about 9 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 20 wt% to about 80 wt%, more preferably about 30 wt% to about 50 wt%. In some preferred embodiments, the brominated flame retardants have a bromine content in the molecule that ranges from about 35 wt% to about 40 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 or inhibition of thermal runaway. 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 required flame-retardant loading is different for different halogenated / brominated sulfite flame retardants, and in some embodiments is usually more than about 10 wt% flame retardant molecules, preferably about 20 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 15 wt% flame retardant molecules, and preferably about 22 wt% relative to the total weight of the nonaqueous electrolyte solution. 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 4 wt% or Attorney Docket No. 1710.00044WO more, preferably about 9 wt% or more, bromine (atoms), relative to the total weight of the nonaqueous electrolyte solution. In other embodiments, the flame-retardant amount is about 4 wt% or more, preferably about 6 wt% or more, more preferably about 9 wt% or more, bromine (atoms), relative to the total weight of the nonaqueous electrolyte solution. In some embodiments, mixtures of two or more halogenated / brominated sulfite flame retardants or halogenated sulfite flame retardants with other halogenated flame retardants or halogenated sulfite flame retardants with other non-halogenated flame retardants can be used in the practice of the presently disclosed subject matter. In the mixtures of two or more 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 mixtures of two or more halogenated / brominated sulfite flame retardants or halogenated sulfite flame retardants with other halogenated flame retardants or halogenated sulfite flame retardants with other non-halogenated flame retardants in a nonaqueous electrolyte solution. Similarly, in one embodiment, the flame- retardant amount of bromine is about 0.01 wt% or more, about 1 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 sulfite flame retardants in the nonaqueous electrolyte solution. In some embodiments of the invention, 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 methyl carbonate 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. Attorney Docket No. 1710.00044WO 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. The halogenated sulfite 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. 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-fcarbon 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 polyoxide 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. 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 Attorney Docket No. 1710.00044WO 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. 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 (l,3- dioxol-2- one), 4-methyl-1,3-dioxol-2-one, and 4,5-dimethyl-1,3-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. 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-containing saturated 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. The tris(trihydrocarbylsilyl) phosphite electrochemical additives contain three to about nine carbon atoms, preferably about three to about six carbon atoms; the Attorney Docket No. 1710.00044WO 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)phos-phite, 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. 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. 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 is preferably 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. 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 Attorney Docket No. 1710.00044WO sulfite), 1,2- propanediol sulfite (1,2-propy1ene sulfite), 4,5-dimethy1-1,3,2- dioxathiolane 2-oxide, 1,3,2-dioxathiane 2-oxide, 4-methyl-1,3-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. 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 I wt% to about 4 wt%, relative to the total weight of the nonaqueous electrolyte solution. 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. Suitable cyclic 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-1,5,2,4- 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. 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 Attorney Docket No. 1710.00044WO 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. 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. 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. The chemical structures for the halogenated sulfite or brominated sulfite compounds, including those used for the disclosed flame retardants and TRIs, are represented by formula (I) and / or formula (II): formula (I), formula (II), wherein R1, R2, R3, and R4 a hydrogen atom, a bromine atom, a C1-C5 bromoalkyl group, or a C2-C5 bromoalkene group, and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2-C5 bromoalkene group comprising at least one bromine atom. In some aspects, two or more of R1, R2, R3, and R4 are a C1-C5 bromoalkyl group comprising at least Attorney Docket No. 1710.00044WO one bromine atom and / or a C2-C5 bromoalkene group comprising at least one bromine atom. Provided in some aspects is an electrolyte additive, where the additive acts as a TRI or flame retardant, and is in some embodiments represented by formula (I) or formula (II): formula (I), formula (II), wherein R1, R2, R3, and R4 a hydrogen atom, a bromine atom, a C1-C5 bromoalkyl group, or a C2-C5 bromoalkene group , and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2-C5 bromoalkene group comprising at least one bromine atom. In some aspects, in the electrolyte additive two or more of R1, R2, R3, and R4 are a C1-C5 bromoalkyl group comprising at least one bromine atom and / or a C2-C5 bromoalkene group comprising at least one bromine atom. In some aspects, the electrolyte additive chemically interferes with flame propagation is fire damping, is flame retarding, and / or is thermal runaway inhibiting. Additionally, provided in some embodiments are electrical energy storage devices comprising a cathode, an anode and an electrolyte. The electrolyte can comprise an aprotic organic solvent system, an alkali metal salt, and an electrolyte additive that chemically interferes with flame propagation. The electrolyte additive is in some embodiments represented by formula (I) or formula (II): , Attorney Docket No. 1710.00044WO formula (II), wherein R1, R2, R3, and R4 a hydrogen atom, a bromine atom, a C1-C5 bromoalkyl group, or a C2-C5 bromoalkene group, and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2-C5 bromoalkene group comprising at least one bromine atom. In some aspects, in the electrical energy storage devices with the electrolyte additive two or more of R1, R2, R3, and R4 are a C1-C5 bromoalkyl group comprising at least one bromine atom and / or a C2-C5 bromoalkene group comprising at least one bromine atom. In some aspects, the electrolyte additive of the electrical energy storage devices chemically interferes with flame propagation is fire damping, is flame retarding, and / or is thermal runaway inhibiting within the electrical energy storage device. In some aspects, the electrolyte additive that chemically interferes with flame propagation is a radical scavenger. In some aspects, the aprotic organic solvent comprises an open-chain or cyclic carbonate, carboxylic acid ester, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono- or polyphosphazene or mixtures thereof. In some aspects, the additive comprises a concentration in the electrolyte of from about 0.01 wt. % to about 50 wt. %. In some embodiments, the electrolyte further comprises an ionic liquid. The ionic liquid can comprise an organic cation comprising N- alkyl-N-alkylpyrrolidinium, N-alkyl-N-alkyl-pyridnium, N-alkyl-Nalkyl-sulfonium, N- alkyl-N-alkyl-ammonium, or N-alkylN-alkyl-piperdinium. Moreover, the ionic liquid can comprise an anion comprising tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, or trifluoroacetate. In some embodiments, the cathode comprises a lithium metal oxide, spinel, olivine, carbon-coated olivine, LiFePO4 , LiCoO2 , LiNiO2 , LiNi1xCoyMetzO2 , LiMn0.5Ni0.5O2, LiMn0.3Co0.3Ni0.3O2, LiMn2O4, LiFeO2, Li1+x’NiaMnbCogMet'dO2-z’,Fz’, Ah’B2(XO4)3(NASICON), vanadium oxide, lithium peroxide, sulfur, polysulfide, a lithium carbon mono fluoride or mixtures of any two or more thereof, where Met is Al, Attorney Docket No. 1710.00044WO 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. In such devices the anode can in some aspects comprise lithium metal, graphitic material, amorphous carbon, Li4Ti5O12, tin alloy, silicon alloy, intermetallic compound or mixtures thereof. Such electrical energy storage devices include, but are not limited to, a lithium battery, lithium-ion battery, lithium-sulfur battery, lithium-air battery, sodium ion battery, magnesium battery, electrochemical cell, capacitor, lithium / MnO2battery, Li / poly(carbon monofluoride) battery, or solar cell. Such devices can in some aspects further comprise a porous separator separating the anode and cathode from each other. The porous separator can include an electron beam-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. In some embodiments, the aprotic organic solvent comprises an open-chain or cyclic carbonate, carboxylic acid ester, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono- or polyphosphazene or mixtures thereof. Additionally, the alkali metal salt comprises a cation selected from the group consisting of lithium, sodium, aluminum and magnesium. Importantly, and unlike previous attempts at making flame retardants or TRI compounds, the electrolyte additive of the presently disclosed subject matter decreases flame propagation in the device while minimally impacting the electrochemical performance of the device, as demonstrated in the Examples herein. For example, the decrease in flame propagation is 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 without the electrolyte additive. Additionally, the electrolyte additive increases inhibition of thermal runaway and / or flame retardancy of the device, wherein the increase is 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 without the electrolyte additive. Finally, the electrochemical performance of the device is maintained at a level of at least about 70%, Attorney Docket No. 1710.00044WO about 75%, about 80%, about 85%, about 90%, about 95% or about 100% of the electrochemical performance of a device without the electrolyte additive. Moreover, provided in some aspects are electrical energy storage systems comprising a first electrical energy storage device as disclosed herein, and a second electrical energy storage device, wherein the second electrical energy storage device is operatively connected to the first electrical energy storage device. Such systems can include a plurality of such energy storage systems where each is operatively connected, and where the thermal runaway potential and / or flammability is markedly decreased. Also provided herein are processes for producing an electrical energy storage device with increased flame retardancy and / or increased thermal runaway inhibition capabilities. Such processes include combining components comprising: i) a cathode; ii) an anode; iii) and an electrolyte. As disclosed herein, the electrolyte can comprise an aprotic organic solvent system, an alkali metal salt, and an electrolyte additive that chemically interferes with flame propagation. The electrolyte additive includes those represented by formula (I) or formula (II) as disclosed herein. The electrolyte may also include where the brominated sulfite selected from the group consisting of 4- (bromomethyl)-1,3,2-dioxathiolane 2-oxide, 4-(bromoethyl)-1,3,2-dioxathiolane 2-oxide, 4-(bromomethyl)-5-methyl-1,3,2-dioxathiolane 2-oxide, 4-(2-bromoethenyl)-1,3,2- dioxathiolane 2-oxide, 4-(1-bromoethenyl)-1,3,2-dioxathiolane 2-oxide, 4-(2-Bromo-2- propen-1-yl)-1,3,2-dioxathiolane 2-oxide, Sulfurous acid, 2-bromomethyl methyl ester and Sulfurous acid, 2-bromoethenyl methyl ester. In such a process the electrolyte additive that chemically interferes with flame propagation can be fire damping, flame retarding, and / or thermal runaway inhibiting. The additive can be added at a concentration in the electrolyte of from about 0.01wt. % to about 50wt. %. The brominated sulfite compounds disclosed herein are further exemplified by the following chemical structures:

[0002] Attorney Docket No. 1710.00044WO have two points of chirality making them diastereomers. Moreover, any of the brominated alkenes may have one or more isomers. As such, when a single structure is shown as above this is intended to represent a mixture of possible isomers, as would be understood by a skilled artisan. By way of illustrative example, and not limitation, 4-(2- bromoethenyl)-1,3,2-dioxathiolane 2-oxide, as shown above, will have the following mixture of isomers: O O Attorney Docket No. 1710.00044WO In such processes and methods, the ingredients and / or components 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 sulfite flame retardant, electrochemical additive(s), and amounts of each component, are as described above. Still another embodiment of the presently disclosed subject matter provides a process for producing an electrolyte solution for an energy storage device and / or 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 sulfite or brominated sulfite flame retardant, as disclosed herein. The presently disclosed subject matter provides nonaqueous electrolyte solutions for lithium-ion batteries and other electrical energy storage devices which contain a halogenated sulfite compound, e.g. a brominated sulfite compound, acting as a flame retardant and / or TRI. In the presence of the halogenated sulfite flame retardant(s), fires are prevented, mitigated and / or extinguished in these nonaqueous electrolyte solutions. In further embodiments, provided are flame retardant compounds comprising 4- (2-bromoethenyl)-1,3,2-dioxathiolane 2-oxide. Such can be used in the disclosed flame retardant compositions, devices and energy storage devices disclosed herein. These flame retardant compounds can increase inhibition of thermal runaway and / or flame retardancy in an environment, e.g. an energy storage device, wherein the increase is 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 environment without the flame retardant compound. Also provided herein are methods of making the brominated sulfite flame retardant compounds. Such methods or processes comprise mixing 4-ethenyl-1,3,2- dioxathiolane 2-oxide and dichloromethane to form a first mixture, adding bromine to the first mixture to form a second mixture, adding triethylamine to the second mixture to form a third mixture, and distilling the third mixture to yield 4-(2-bromoethenyl)-1,3,2- dioxathiolane 2-oxide. Distilling the third mixture can further comprise removing solvent from the third mixture via rotary evaporator, and passing a residual solution through a silica gel column under vacuum. Further details of such methods are disclosed in the Examples. Attorney Docket No. 1710.00044WO Examples 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 4-(2-bromoethenyl)-1,3,2-dioxathiolane 2-oxide In a 250 mL round bottle flask, a mixture of 26.8g 4-ethenyl-1,3,2-dioxathiolane 2-oxide (0.2mol) and 100mL dichloromethane were magnetically stirred in ice-cold water. 32g bromine (0.2mol) was then slowly added to the flask using peristaltic pump. After the complete addition of bromine, the reaction mixture was stirred at room temperature for 2h. Subsequently, the reaction flask was placed in ice-cold water, and 24g triethylamine (0.24mol) was added dropwise using an additional funnel. After the addition of all triethylamine, the reaction mixture was stirred at room temperature overnight. The solid was filtered, and the remaining solution was collected in 250mL round flask. The solvent was removed using a rotary evaporator, and the residual solution was then passed through a silica gel column and subjected to vacuum distillation, resulting 24.71g (58% yield) of 4-(2-bromoethenyl)-1,3,2-dioxathiolane 2- oxide. Example 2- Flame retardancy (UL-94) testing 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 (l 2.7 ± 0.2.5 cm) long. 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., Attorney Docket No. 1710.00044WO 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 LiPF6 in ethylene carbonate / ethyl methyl carbonate (wt ratio 3:7). Each wick was soaked in the electrolyte solution for 30 minutes. 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. The burner was ignited and adjusted to produce a blue flame 20 ± 1 mm high. 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. If an exhaust fan was running, it was shut off for the test. 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 horizotal. 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 l inch (2.54 cm) mark to the 4 inch (10.16 cm) mark. 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. Results of the UL-94 flame retardancy testing of the disclosed brominated sulfite flame retardants are summarized in Table 1. Attorney Docket No. 1710.00044WO Table 1. UL-94 Testing Result Flame retardant. Flame retardant Time to As the results show, the brominated sulfite flame retardants of the presently disclosure provided effective flame retardancy sufficient to be considered a flame retardant for use in energy storage devices and batteries. This is particularly evident when compared to the comparative example where chlorine replaces bromine (last row in Table. 1) which, in contrast to bromine, is flammable. Example 3- Coin cell testing Tests of some nonaqueous electrolyte solutions containing flame retardant additives as disclosed herein in coin cells were also carried out. Coin cells with an areal capacity of roughly 2 mAh / cm2were assembled using nonaqueous electrolyte solutions containing the desired amount of flame retardant 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. See Table 2A. Attorney Docket No. 1710.00044WO Table 2A. Coulombic efficiency Chemical NameFlame retardant inelectrolyte solution 1st c cle 10th c cle sed in lithium-ion batteries with no flame retardant (control); b) an electrolyte solution with 4-(Bromomethyl)-1,3,2-dioxathiolane 2-oxide + 2% LiDFOB, and c) a second control (same as control) plus 2% LiDFOB. Results of Coulombic Efficiency measurements up to 501 cycles are shown in Table 2B. Table 2B. Coulombic Efficiency Cycles 2 21 51 101 201 301 401 501 % % % 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 4-(Bromomethyl)-1,3,2- dioxathiolane 2-oxide+ 2% LiDFOB. Finally, a second comparative example included the control electrolyte (same as comparative example 1) plus 2% LiDFOB to confirm that Attorney Docket No. 1710.00044WO the results observed with the 4-(Bromomethyl)-1,3,2-dioxathiolane 2-oxide + 2% LiDFOB test sample was not due to the addition of LiDFOB. Comparative capacity retention were measured and recorded over increasing numbers of cycles up to 1001 cycles. Results are summarized in Table 3 below. Table 3. Long Term Cycling (Capacity Retention) Comparative Comparative 4 B th l 1 2 As the data in Table 3 shows, while the capacity retention of comparative example 1 (control) steadily decreased as the number of cycles increased (77% at 101 cycles, down to 66% at 501 cycles), the capacity retention observed with the electrolyte Attorney Docket No. 1710.00044WO solution having the flame retardant ( 4-(Bromomethyl)-1,3,2-dioxathiolane 2-oxide+ 2% LiDFOB) surprisingly maintained a high level of efficiency even at 1001 cycles. Summary and Conclusions from Examples 2 and 3 The data in the Examples illustrates the effectiveness of the disclosed brominated sulfite 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 brominated sulfite flame retardants appears to have maintained and / or increased the level of performance over time as compared to nonaqueous electrolyte solutions without the brominated sulfite flame retardants. 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

Attorney Docket No. 1710.00044WO CLAIMS What is claimed is:

1. An electrical energy storage device comprising: a cathode; an anode; and an electrolyte, the electrolyte comprising: an aprotic organic solvent system; an alkali metal salt; and an electrolyte additive that chemically interferes with flame propagation, the electrolyte additive represented by formula (I) or formula (II): formula (I), formula (II),wherein R1, R2, R3, and R4 are independently a hydrogen atom, a bromine atom, a C1-C5 bromoalkyl group, or a C2-C5 bromoalkene group, and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2- C5 bromoalkene group comprising at least one bromine atom.

2. The device of claim 1, wherein two or more of R1, R2, R3, and R4 are a C1- C5 bromoalkyl group comprising at least one bromine atom and / or a C2-C5 bromoalkene group comprising at least one bromine atom.

3. The device of any of claims 1 to 2, wherein the electrolyte additive that chemically interferes with flame propagation is fire damping, flame retarding, and / or thermal runaway inhibiting.Attorney Docket No. 1710.00044WO 4. The device of any of claims 1 to 3, wherein the electrolyte additive that chemically interferes with flame propagation is a radical scavenger.

5. The device of any of claims 1 to 4, wherein the aprotic organic solvent comprises an open-chain or cyclic carbonate, carboxylic acid ester, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono- or polyphosphazene or mixtures thereof.

6. The device of any of claims 1 to 5, wherein the additive comprises a concentration in the electrolyte of from about 0.01 wt. % to about 50wt. %.

7. The device of any of claims 1 to 6, wherein the electrolyte further comprises an ionic liquid.

8. The device of claim 7, wherein the ionic liquid comprises an organic cation comprising N-alkyl-N-alkylpyrrolidinium, N-alkyl-N-alkyl-pyridnium, N-alkyl- Nalkyl-sulfonium, N-alkyl-N-alkyl-ammonium, or N-alkylN-alkyl-piperdinium.

9. The device of claim 7, wherein the ionic liquid comprises an anion comprising tetrafluoroborate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide, or trifluoroacetate.

10. The device of any of claims 1 to 9, wherein the cathode comprises a lithium metal oxide, spinel, olivine, carbon-coated olivine, LiFePO4, LiCoO2, LiNiO2, LiNi1xCoyMetzO2 , LiMn0.5Ni0.5O2 , LiMn0.3Co0.3Ni0.3O2, LiMn2O4 , LiFeO2 , Li1+x’NiaMnbCogMet'dO2-z’,Fz’, Ah’B2(XO4)3(NASICON), vanadium oxide, lithium peroxide, 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.Attorney Docket No. 1710.00044WO 11. The device of any of claims 1 to 10, wherein the anode comprises lithium metal, graphitic material, amorphous carbon, Li4Ti5O12, tin alloy, silicon alloy, intermetallic compound or mixtures thereof.

12. The device of any of claims 1 to 11, wherein the device comprises a lithium battery, lithium-ion battery, lithium-sulfur battery, lithium-air battery, sodium ion battery, magnesium battery, electrochemical cell, capacitor, lithium / MnO2 battery, Li / poly(carbon monofluoride) battery, or solar cell.

13. The device of any of claims 1 to 12, further comprising a porous separator separating the anode and cathode from each other.

14. The device of claim 12, wherein the porous separator comprises an electron beam-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.

15. The device of any of claims 1 to 14, wherein the aprotic organic solvent comprises an open-chain or cyclic carbonate, carboxylic acid ester, nitrite, ether, sulfone, ketone, lactone, dioxolane, glyme, crown ether, siloxane, phosphoric acid ester, phosphite, mono- or polyphosphazene or mixtures thereof.

16. The device of any of claims 1 to 15, wherein the alkali metal salt comprises a cation selected from the group consisting of lithium, sodium, aluminum and magnesium.

17. The device of any of claims 1 to 16, wherein the electrolyte additive decreases flame propagation in the device while minimally impacting the electrochemical performance of the device.Attorney Docket No. 1710.00044WO 18. The device of claim 16, wherein the decrease in flame propagation is 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 without the electrolyte additive.

19. The device of any of claims 1 to 16, wherein the electrolyte additive increases inhibition of thermal runaway and / or flame retardancy of the device, wherein the increase is 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 without the electrolyte additive.

20. The device of any of claims 16 to 19, wherein the electrochemical performance of the device is maintained at a level of at least about 70%, about 75%, about 80%, about 85%, about 90%, about 95% or about 100% of the electrochemical performance of a device without the electrolyte additive.

21. An electrical energy storage system comprising: a first electrical energy storage device of any of claims 1 to 20; and a second electrical energy storage device, wherein the second electrical energy storage device is operatively connected to the first electrical energy storage device.

22. A process for producing an electrical energy storage device with increased flame retardancy and / or increased thermal runaway inhibition, which process comprises combining components comprising: i) a cathode; ii) an anode; iii) and an electrolyte, the electrolyte comprising: an aprotic organic solvent system; an alkali metal salt; and an electrolyte additive that chemically interferes with flame propagation, the electrolyte additive represented by formula (I) or formula (II):Attorney Docket No. 1710.00044WO formula (I), formula (II),wherein R1, R2, R3, and R4 are independently a hydrogen atom, a bromine atom, a C1-C5 bromoalkyl group, or a C2-C5 bromoalkene group, and wherein at least one of R1, R2, R3, and R4 is a C1-C5 bromoalkyl group comprising at least one bromine atom or a C2- C5 bromoalkene group comprising at least one bromine atom.

23. The process of claim 21, wherein the electrolyte additive that chemically interferes with flame propagation is fire damping, flame retarding, and / or thermal runaway inhibiting.

24. The process of any of claims 21 to 22, wherein the additive comprises a concentration in the electrolyte of from about 0.01 wt. % to about 50wt. %.

25. The process of any of claims 21 to 23, wherein the electrolyte additive decreases flame propagation in the device while minimally impacting the electrochemical performance of the device.

26. The process of any of claims 21 to 24, wherein the decrease in flame propagation and / or flammability is at least about 25%, 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 without the electrolyte additive.

27. The process of any of claims 21 to 25, wherein the electrolyte additive increases inhibition of thermal runaway and / or flame retardancy of the device, wherein the increase is at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least aboutAttorney Docket No. 1710.00044WO 90%, at least about 95%, or more as compared to an electrical energy storage device without the electrolyte additive.

28. A flame retardant compound, the flame retardant compound comprising 4-(2- bromoethenyl)-1,3,2-dioxathiolane 2-oxide.

29. The flame retardant compound of claim 28, wherein the flame retardant compound increases inhibition of thermal runaway and / or flame retardancy in an environment, wherein the increase is 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 environment without the flame retardant compound, optionally wherein the environment is an electrical energy storage device.

30. A method of making the flame retardant compound of claims 28 or 29, the method comprising: mixing 4-ethenyl-1,3,2-dioxathiolane 2-oxide and dichloromethane to form a first mixture; adding bromine to the first mixture to form a second mixture; adding triethylamine to the second mixture to form a third mixture; and distilling the third mixture to yield 4-(2-bromoethenyl)-1,3,2-dioxathiolane 2-oxide.

31. The method of claim 30, wherein distilling the third mixture comprises removing solvent from the third mixture via rotary evaporator, and passing a residual solution through a silica gel column under vacuum.