Flame retardants for lithium batteries

Abstract

The present invention provides a non-aqueous electrolyte solution for a lithium battery containing one or more brominated flame retardants. The non-aqueous electrolyte solution includes: a) a liquid electrolyte medium; b) a lithium-containing salt; and c) at least one brominated flame retardant. The brominated flame retardant is present in the electrolyte solution in a flame-retarding amount.

Description

[Technical field]

[0001] The present invention relates to a flame retardant for lithium batteries. [Background technology]

[0002] One of the components that affects the safety of lithium-ion batteries is the use of flammable solvents in lithium-containing electrolyte solutions. The inclusion of a flame retardant in the electrolyte solution is one way to mitigate flammability. For a flame retardant to be a suitable component of the electrolyte solution, in addition to being soluble in the electrolyte solution, it must be electrochemically stable over the battery operating range and have minimal adverse effects on battery performance. Adverse effects on battery performance can include reduced electrical conductivity and / or chemical instability with respect to the active materials.

[0003] What is desired is a flame retardant that can effectively suppress flammability while minimizing the impact on the electrochemical performance of lithium ion batteries at a reasonable cost. Summary of the Invention

[0004] The present invention provides a non-aqueous electrolyte solution for a lithium battery that includes at least one brominated flame retardant, wherein, in the presence of the brominated flame retardant(s), ignition in such a non-aqueous electrolyte solution is extinguished, at least under laboratory conditions.

[0005] One embodiment of the invention is a non-aqueous electrolyte solution for a lithium battery comprising I) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) a flame retardant amount of A) tribromoethylene or tribromonopentyl alcohol, or B) a) a mixture of 1,2 dibromoethane and tribromoethylene in a weight ratio of about 0.75:1 to about 3:1, or b) a mixture of tribromoethylene and 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine in a weight ratio of 0.75:1 to about 2.25:1.

[0006] When the material present in a flame retardant amount is A) tribromoethylene or tribromoneopentyl alcohol, optionally, iv) at least one electrochemical additive is present selected from a) unsaturated cyclic carbonates containing 3 to about 6 carbon atoms, b) fluorine-containing saturated cyclic carbonates containing 3 to about 5 carbon atoms and 1 to about 4 fluorine atoms, c) tris(trihydrocarbylsilyl)phosphites containing 3 to about 9 carbon atoms, d) trihydrocarbyl phosphates containing 3 to about 12 carbon atoms, e) cyclic sultones containing 3 to about 8 carbon atoms, f) saturated cyclic hydrocarbyl sulfites having 5- or 6-membered rings and containing 2 to about 6 carbon atoms, g) saturated cyclic hydrocarbyl sulfates having 5- or 6-membered rings and containing 2 to about 6 carbon atoms, h) cyclic dioxadithio polyoxide compounds having 6-, 7-, or 8-membered rings and containing 2 to about 6 carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing.

[0007] These and other embodiments and features of the present invention will become further apparent from the following description and appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In this specification, the term "electrolyte solution" is used interchangeably with the term "non-aqueous electrolyte solution."

[0009] Liquid electrolyte medium for lithium electrolyte solution used in lithium batteries The solvent typically comprises one or more solvents that form a cyclic carbonate, which are polar, aprotic, stable to electrochemical cycling, and preferably have low viscosity. Such solvents typically include acyclic carbonates, cyclic carbonates, ethers, sulfur-containing compounds, and esters of boric acid.

[0010] Solvents from which the liquid electrolyte medium can be formed in the practice of the invention include ethylene carbonate (1,3-dioxolan-2-one), dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dioxolane, dimethoxyethane (glyme), tetrahydrofuran, methanesulfonyl chloride, 1,3,2-dioxathiolane 2-oxide (ethylene sulfite), 1,3-propylene glycol borate, and mixtures of any two or more of the foregoing.

[0011] Preferred solvents include ethylene carbonate, ethyl methyl carbonate, and mixtures thereof. More preferred is a mixture of ethylene carbonate and ethyl methyl carbonate, particularly a mixture in which the volume ratio of ethylene carbonate:ethyl methyl carbonate is in the range of about 20:80 to about 40:60, more preferably about 25:75 to about 35:65.

[0012] Lithium-containing salts suitable for use in the practice of the present invention include lithium chloride, lithium bromide, lithium iodide, lithium perchlorate, lithium nitrate, lithium thiocyanate, lithium aluminate, lithium tetrachloroaluminate, and lithium tetrafluoroaluminate. Examples of the lithium salt include lithium tetraphenylborate, lithium tetrafluoroborate, lithium bis(oxalato)borate (LiBOB), lithium di(fluoro)(oxalato)borate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium titanate, lithium manganate, lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium alkyl carbonate with an alkyl group having 1 to 6 carbon atoms, lithium methylsulfonate, lithium trifluoromethylsulfonate, lithium pentafluoroethylsulfonate, lithium pentafluorophenylsulfonate, lithium fluorosulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium (ethylsulfonyl)(trifluoromethylsulfonyl)imide, and mixtures of any two or more of the above. Examples of preferred lithium-containing salts include lithium hexafluorophosphate and lithium bis(oxalato)borate.

[0013] A typical concentration of the lithium-containing salt in the electrolyte solution is within 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 further preferably about 0.95 M to about 1.5 M. When a plurality of lithium-containing salts form a lithium-containing electrolyte, the concentration refers to the total concentration of all the lithium-containing salts present in the electrolyte solution.

[0014] The electrolyte may contain other salts in addition to lithium salts, provided that such other salt(s) do not substantially reduce either the performance of the battery in the desired application or the flame retardancy of the electrolyte solution.Suitable electrolytes other than lithium salts include other alkali metal salts, such as sodium salts, potassium salts, rubidium salts, and cesium salts, and alkaline earth metal salts, such as magnesium salts, calcium salts, strontium salts, and barium salts.In some embodiments, the only salt in the non-aqueous electrolyte solution is one or more lithium salts.

[0015] Suitable alkali metal salts that may be present in the electrolyte solution include sodium salts (e.g., sodium chloride, sodium bromide, sodium iodide, sodium perchlorate, sodium nitrate, sodium phosphate, sodium phosphate salts ... salts (e.g., 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), and potassium salts (e.g., 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).

[0016] Suitable alkaline earth metal salts that may be present in the electrolyte solution include magnesium salts (e.g., 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 (e.g., calcium chloride, calcium bromide, calcium iodide, calcium perchlorate, calcium nitrate, calcium thiocyanate, calcium aluminate, calcium tetrachloroaluminate, calcium tetrafluoroaluminate, calcium tetraphenylborate, calcium tetrafluoroborate, calcium hexafluorophosphate).

[0017] In the practice of the present invention, the flame retardant is miscible with the liquid medium of the non-aqueous electrolyte solution ("miscible" means that the flame retardant does not form a separate phase from the electrolyte solution). More specifically, in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate with 1.2 M lithium hexafluorophosphate, the flame retardant is miscible if it forms a single phase after shaking on a shaker for 24 hours, does not form a separate phase after shaking is stopped, does not precipitate from the non-aqueous electrolyte solution, and forms a suspension or slurry. It is recommended and preferred that the brominated flame retardant does not cause precipitation of other components of the non-aqueous electrolyte solution or the formation of a suspension or slurry.

[0018] In the practice of the present invention, a mixture of two or more brominated flame retardants can be used. In the mixture of brominated flame retardants, one component is 1,2-dibromoethane and the other component is tribromoethylene. In the mixture, the weight ratio of 1,2-dibromoethane:tribromoethylene is in the range of about 0.75:1 to about 3:1, more preferably about 1:1 to about 3:1, and even more preferably about 1:1 to about 2.5:1.

[0019] In a mixture of two or more brominated flame retardants, the flame retardant amount is about 6 wt% or more of the flame retardant molecules based on the total weight of the non-aqueous electrolyte solution, where this amount refers to the total amount of the brominated flame retardant molecules in the non-aqueous electrolyte solution, particularly when the weight ratio of 1,2-dibromoethane:tribromoethylene is in the range of about 0.75:1 to about 1.25:1. In another embodiment, the flame retardant amount is about 20 wt% or more of the flame retardant molecules based on the total weight of the non-aqueous electrolyte solution, where this amount refers to the total amount of the brominated flame retardant molecules in the non-aqueous electrolyte solution, particularly when the weight ratio of 1,2-dibromoethane:tribromoethylene is in the range of about 2:1 to about 2.5:1.

[0020] The electrolyte solution may optionally contain one or more non-brominated flame retardants. Such other flame retardants are generally fluorinated cyclotriphosphinine derivatives, such as 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine and 2-ethoxy-2,4,4,6,6-pentafluorotriphosphinine. A preferred non-brominated flame retardant is 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine.

[0021] In the mixture with the non-brominated flame retardant, the brominated flame retardant is tribromoethylene, and the non-brominated flame retardant is 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine. In the mixture with these non-brominated flame retardants, the weight ratio of tribromoethylene to 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine is about 0.75:1 to about 2.25:1, preferably about 0.75:1 to about 2:1, more preferably about 0.9:1 to about 1.5:1.

[0022] When a non-brominated flame retardant is used, the amount of flame retardant is about 4 wt% or more of flame retardant molecules relative to the total weight of the non-aqueous electrolyte solution, where this amount refers to the total amount of brominated flame retardant and non-brominated flame retardant in the non-aqueous electrolyte solution. In a preferred embodiment, particularly when the weight ratio of tribromoethylene:2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine is within the range of about 0.75:1 to about 1.25:1, or within the range of about 1.5:1 to about 2:1, the amount of flame retardant is about 4 wt% or more of flame retardant molecules relative to the total weight of the non-aqueous electrolyte solution.

[0023] In some embodiments of the present invention, at least one electrochemical additive is included in the non-aqueous electrolyte solution along with tribromoethylene or tribromoneopentyl alcohol.

[0024] In the practice of the invention, the amount of flame retardant in a non-aqueous electrolyte solution means that there is enough flame retardant present such that the solution passes the modified horizontal UL-94 test described below. Preferred flame retardants also pass the heat abuse test described below. Different flame retardants and combinations of flame retardants will have different amounts of flame retardant. For tribromoethylene, the amount of flame retardant is typically greater than about 4 wt% of flame retardant molecules, preferably greater than about 6 wt% of flame retardant molecules, more preferably greater than about 8 wt% of flame retardant molecules. More preferably, the amount of flame retardant for tribromoethylene is between about 8 wt% and about 10 wt% of flame retardant molecules. In some embodiments, for tribromoethylene, the amount of flame retardant is preferably greater than about 10 wt% of flame retardant molecules by weight of the total non-aqueous electrolyte solution, and in other embodiments, the amount of flame retardant is preferably greater than about 15 wt% of flame retardant molecules by weight of the total non-aqueous electrolyte solution. In the case of tribromoneopentyl alcohol, the flame retardant amount is greater than about 10 wt % of the flame retardant molecule, preferably greater than about 15 wt % of the flame retardant molecule, based on the total weight of the non-aqueous electrolyte solution.

[0025] The flame retardant level in terms of bromine content (the amount that passes the modified horizontal UL-94 test described below) of a non-aqueous electrolyte solution is typically greater than or equal to about 5 wt% bromine (atomic) by weight of the total solution when the flame retardant is tribromoethylene, and is typically greater than or equal to about 8 wt% bromine (atomic) by weight of the total solution when the flame retardant is tribromoneopentyl alcohol.

[0026] In some embodiments, the flame retardant value of tribromoethylene is about 5.4 wt% bromine (atomic) or more based on the total weight of the non-aqueous electrolyte solution. Preferably, for tribromoethylene, the flame retardant value in terms of bromine content is about 7 wt% bromine (atomic) or more, preferably about 9 wt% bromine (atomic) or more based on the total weight of the non-aqueous electrolyte solution.

[0027] In another embodiment, the flame retardant content of tribromoneopentyl alcohol is greater than or equal to about 9 wt % bromine (atomic) based on the total weight of the non-aqueous electrolyte solution, preferably greater than or equal to about 10 wt % bromine (atomic) based on the total weight of the non-aqueous electrolyte solution, and more preferably greater than or equal to about 12 wt % bromine (atomic) based on the total weight of the non-aqueous electrolyte solution.

[0028] In the practice of the present invention, the electrochemical additive is soluble or miscible in the liquid medium of the non-aqueous electrolyte solution. The electrochemical additive is miscible with the electrolyte medium. Here, "miscible" means that the electrochemical additive does not form a separate phase from the electrolyte solution. More specifically, in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate containing 1.2 M lithium hexafluorophosphate, if the electrochemical additive forms a single phase after shaking on a shaker for 24 hours, does not form a separate phase after shaking is stopped, does not precipitate from the non-aqueous electrolyte solution, and forms a suspension or slurry, the electrochemical additive is miscible.

[0029] The term "soluble" is usually used for electrochemical additives in solid form to indicate that the electrochemical additive does not precipitate or form a suspension or slurry from the non-aqueous electrolyte solution once dissolved. More specifically, in a mixture of 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate containing 1.2 M lithium hexafluorophosphate, if the electrochemical additive dissolves after shaking on a shaker for 24 hours and no precipitate, suspension or slurry is formed after shaking is stopped, the electrochemical additive is soluble. It is recommended and preferred that the electrochemical additive does not cause precipitation of other components of the non-aqueous electrolyte solution or the formation of a suspension or slurry.

[0030] The brominated flame retardants, electrochemical additives, and mixtures thereof are generally stable to electrochemical cycling and preferably have low viscosity and / or do not significantly increase the viscosity of the non-aqueous electrolyte solution.

[0031] In various embodiments, the electrochemical additive is selected from a) unsaturated cyclic carbonates containing 3 to about 4 carbon atoms, b) fluorine-containing saturated cyclic carbonates containing 3 to about 4 carbon atoms and 1 to about 2 fluorine atoms, c) tris(trihydrocarbylsilyl)phosphites containing 3 to about 6 carbon atoms, d) trihydrocarbyl phosphates containing 3 to about 9 carbon atoms, e) cyclic sultones containing 3 to about 4 carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered ring and containing 2 to about 4 carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered ring and containing 2 to about 4 carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6- or 7-membered ring and containing 2 to about 4 carbon atoms, i) another lithium-containing salt, and j) a mixture of any two or more of the foregoing.

[0032] In another embodiment, the electrochemical additive comprises: a) about 0.5 wt % to about 12 wt % of an unsaturated cyclic carbonate (amount based on the total weight of the non-aqueous electrolyte solution); b) about 0.5 wt % to about 15 wt % of a fluorine-containing saturated cyclic carbonate (amount based on the total weight of the non-aqueous electrolyte solution); c) about 0.1 wt % to about 5 wt % of a tris(trihydrocarbylsilyl)phosphite (amount based on the total weight of the non-aqueous electrolyte solution); d) about 0.5 wt % to about 5 wt % of a trihydrocarbyl phosphate (amount based on the total weight of the non-aqueous electrolyte solution); e) about 0.25 wt % to about 5 wt % of a cyclic sultone. (amount based on the total weight of the non-aqueous electrolyte solution), f) about 0.5 wt % to about 5 wt % of a saturated cyclic hydrocarbyl sulfite (amount based on the total weight of the non-aqueous electrolyte solution), g) about 0.25 wt % to about 5 wt % of a saturated cyclic hydrocarbyl sulfate (amount based on the total weight of the non-aqueous electrolyte solution), h) about 0.5 wt % to about 5 wt % of a cyclic dioxadithio polyoxide compound (amount based on the total weight of the non-aqueous electrolyte solution), i) about 0.5 wt % to about 5 wt % of another lithium-containing salt (amount based on the total weight of the non-aqueous electrolyte solution), and j) a mixture of any two or more of the foregoing.

[0033] In some embodiments, the electrochemical additive is an unsaturated cyclic carbonate containing from 3 to about 6 carbon atoms, preferably from 3 to about 4 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-1,3-dioxol-2-one, with vinylene carbonate being the preferred unsaturated cyclic carbonate. The amount of unsaturated cyclic carbonate is preferably about 0.5% by weight based on the total weight of the non-aqueous electrolyte solution. % to about 12 wt%, and more preferably about 0.5 wt% to about 3 wt% or about 8 wt% to about 11 wt%.

[0034] When the electrochemical additive is a fluorine-containing saturated cyclic carbonate containing 3 to about 5 carbon atoms, preferably 3 to about 4 carbon atoms, and 1 to about 4 fluorine atoms, preferably 1 to about 2 fluorine atoms, suitable fluorine-containing saturated cyclic carbonates include 4-fluoroethylene carbonate and 4,5-difluoroethylene carbonate. Preferably, the fluorine-containing saturated cyclic carbonate is 4-fluoro-ethylene carbonate. The amount of the fluorine-containing saturated cyclic carbonate is preferably about 0.5 wt% to about 15 wt%, more preferably about 5 wt% to about 12 wt%, based on the total weight of the non-aqueous electrolyte solution.

[0035] The tris(trihydrocarbylsilyl)phosphite electrochemical additive contains 3 to about 9 carbon atoms, preferably about 3 to about 6 carbon atoms, and the trihydrocarbylsilyl groups may be the same or different. Suitable tris(trihydrocarbylsilyl)phosphites include tris(trimethylsilyl)phosphite, bis(trimethylsilyl)(triethylsilyl)phosphite, tris(trimethylsilyl)phosphite, bis(trimethylsilyl)(tri-n-propylsilyl)phosphite, and tris(tri-n-propylsilyl)phosphite, with tris(trimethylsilyl)phosphite being the preferred tris(trihydrocarbylsilyl)phosphite. The amount of tris(trihydrocarbylsilyl)phosphite is preferably about 0.1 wt% to about 5 wt%, more preferably about 0.15 wt% to about 4 wt%, and even more preferably about 0.2 wt% to about 3 wt% based on the total weight of the non-aqueous electrolyte solution.

[0036] In some embodiments, the electrochemical additive is a trihydrocarbyl phosphate containing 3 to about 12 carbon atoms, preferably 3 to about 9 carbon atoms. The hydrocarbyl groups may 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, dimethylethyl phosphate, tri-n-propyl phosphate, triallyl phosphate, and trivinyl phosphate, with triallyl phosphate being the preferred trihydrocarbyl phosphate. The amount of trihydrocarbyl phosphate is typically about 0.5 wt% to about 5 wt%, preferably about 1 wt% to about 5 wt%, and more preferably about 2 wt% to about 4 wt%, based on the total weight of the non-aqueous electrolyte solution.

[0037] When the electrochemical additive is a cyclic sultone containing 3 to about 8 carbon atoms, preferably 3 to about 4 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-1,2-benzoxathiol 2,2-dioxide), and 1,8-naphthosultone. Preferred cyclic sultones include 1,3-propane sultone and 1,3-propene sultone. The amount of the cyclic sultone is preferably about 0.25 wt % to about 5 wt %, and more preferably about 0.5 wt % to about 4 wt %, based on the total weight of the nonaqueous electrolyte solution.

[0038] The saturated cyclic hydrocarbyl sulfite electrochemical additive contains from 2 to about 6 carbon atoms, preferably from 2 to about 4 carbon atoms, and has a 5- or 6-membered ring, preferably a 5-membered ring. There may be one or more substituents on the ring, such as methyl or ethyl groups, preferably one or more methyl groups, but it is more preferred that there are no substituents on the ring. Suitable saturated rings Examples of the cyclic hydrocarbyl sulfite include 1,3,2-dioxathiolane 2-oxide (1,2-ethylene sulfite), 1,2-propanediol sulfite (1,2-propylene sulfite), 4,5-dimethyl-1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiane 2-oxide, and 4-methyl-1,3-dioxathiane 2-oxide (1,3-butylene sulfite). Examples of the preferred cyclic hydrocarbyl sulfite include 1,3,2-dioxathiolane 2-oxide. The amount of the cyclic hydrocarbyl sulfite is preferably about 0.5 wt% to about 5 wt%, more preferably about 1 wt% to about 4 wt%, based on the total weight of the nonaqueous electrolyte solution.

[0039] In some embodiments, the electrochemical additive is a saturated cyclic hydrocarbyl sulfate containing 2 to about 6 carbon atoms, preferably 2 to about 4 carbon atoms, and having a 5- or 6-membered ring, preferably a 5-membered ring. One or more substituents, such as methyl or ethyl groups, preferably one or more methyl groups, may be present on the ring, but more preferably there are no substituents on the ring. 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 amount of the saturated cyclic hydrocarbyl sulfate is preferably about 0.25 wt % to about 5 wt %, and more preferably about 1 wt % to about 4 wt %, based on the total weight of the non-aqueous electrolyte solution.

[0040] When the electrochemical additive is a cyclic dioxadithiopolyoxide compound, the cyclic dioxadithiopolyoxide compound contains 2 to about 6 carbon atoms, preferably 2 to about 4 carbon atoms, and has a 6-, 7-, or 8-membered ring. Preferably, the cyclic dioxadithiopolyoxide compound contains 2 to about 4 carbon atoms and has a 6- or 7-membered ring. One or more substituents, such as methyl or ethyl groups, preferably one or more methyl groups, may be present on the ring, but it is more preferred that there are no substituents 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-tetroxide (cyclodisone), 3-methyl-1,5,2,4-dioxadithiepane 2,2,4,4-tetroxide, and 1,5,2,4-dioxadithiocane 2,2,4,4-tetroxide, with 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide being preferred. The amount of the cyclic dioxadithio polyoxide compound is preferably about 0.5wt% to about 5wt%, more preferably about 1wt% to about 4wt%, based on the total weight of the non-aqueous electrolyte solution.

[0041] The terms "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, the amount of the electrochemical additive is preferably about 0.5 wt% to about 5 wt% based on the total weight of the non-aqueous electrolyte solution. Suitable lithium-containing salts include all the lithium-containing salts listed above, with lithium bis(oxalato)borate being preferred.

[0042] A mixture of any two or more of the aforementioned electrochemical additives (including different electrochemical additives of the same type and / or different types of electrochemical additives) can be used. When a mixture of electrochemical additives is used, the total amount of electrochemical additives is about 0.25 wt% to about 5 wt% based on the total weight of the non-aqueous electrolyte solution. A mixture of an unsaturated cyclic carbonate and a saturated cyclic hydrocarbyl sulfite, or a mixture of a cyclic sultone, a tris(trihydrocarbylsilyl)phosphite, and a cyclic dioxadithio polyoxide compound is preferred.

[0043] Preferred types of electrochemical additives, especially when not used with other electrochemical additives, include saturated cyclic hydrocarbyl sulfates, cyclic sultones, tris(trihydrocarbylsilyl)phosphites, and other lithium-containing salts. More preferably, the amount of saturated cyclic hydrocarbyl sulfates is about 1 wt% to about 4 wt%, the amount of cyclic sultones is about 0.5 wt% to about 4 wt%, the amount of tris(trihydrocarbylsilyl)phosphites is about 0.2 wt% to about 3 wt%, and the amount of other lithium-containing salts is about 1 wt% to about 4 wt%, respectively, based on the total weight of the non-aqueous electrolyte solution.

[0044] In other embodiments, the electrochemical additive is selected from vinylene carbonate, 4-fluoroethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1-propane-1,3-sultone, 1-propene-1,3-sultone, 1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium bis(oxalato)borate, lithium hexafluorophosphate, and mixtures of any two or more thereof. The electrochemical additive is preferably vinylene carbonate, 1,3,2-dioxathiolane 2,2-dioxide, 1-propane-1,3-sultone, 1-propene-1,3-sultone, tris(trimethylsilyl)phosphite, or lithium bis(oxalato)borate, more preferably 1,3,2-dioxathiolane 2,2-dioxide, 1-propene-1,3-sultone, or lithium bis(oxalato)borate. More preferred electrochemical additives are 1,3,2-dioxathiolane 2,2-dioxide and lithium bis(oxalato)borate. The amount and preference of these are as described above.

[0045] A mixture of two or more of the foregoing electrochemical additives can be used. When a mixture of electrochemical additives is used, the total amount of electrochemical additives is about 0.25 wt % to about 5 wt % based on the total weight of the non-aqueous electrolyte solution.

[0046] Additional components that are often included in electrolyte solutions for lithium batteries can also be present in the electrolyte solution of the present invention. Such additional components include succinonitrile and silazane compounds (e.g., hexamethyldisilazane). Typically, the amount of the optional components is in the range of about 1 wt% to about 5 wt%, preferably about 2 wt% to about 4 wt%, based on the total weight of the non-aqueous electrolyte solution.

[0047] Another embodiment of the present invention provides a method for producing a non-aqueous electrolyte solution for a lithium battery. The method includes combining components including: i) a liquid electrolyte medium; ii) a lithium-containing salt; iii) tribromoethylene or tribromoneopentyl alcohol; and optionally iv) at least one electrochemical additive as described above. The tribromoethylene or tribromoneopentyl alcohol is present in the electrolyte solution in a flame retardant amount. The components can be combined in any order, but it is preferred that all components are added to the liquid electrolyte medium. It is also preferred that the optional components are added to the liquid electrolyte medium. The characteristics and preferences of the liquid electrolyte medium, the lithium-containing salt, the flame retardant, the electrochemical additive(s), and the amounts of each component are as described above.

[0048] In some preferred embodiments of the present invention in which an electrochemical additive is used, the electrochemical additive is selected from the group consisting of vinylene carbonate, 4-fluoroethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1-propane-1,3-sultone, 1-propene-1,3-sultone, 1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium bis(oxalato)borate, hexafluorolithium, tetrafluoroethylene carbonate ... lithium phosphate, and mixtures of any two or more thereof.

[0049] Another embodiment of the present invention provides a method for producing a non-aqueous electrolyte solution for a lithium battery, comprising combining components including: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) a flame retardant amount of a) a mixture of 1,2 dibromoethane and tribromoethylene in a weight ratio of about 0.75:1 to about 3:1, or b) a mixture of tribromoethylene and 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine in a weight ratio of 0.75:1 to about 2.25:1. The characteristics and preferences of the liquid electrolyte medium, the lithium-containing salt, the flame retardant, and the amounts of each component are as described above.

[0050] The non-aqueous electrolyte solution of the present invention containing one or more brominated flame retardants is typically used in a non-aqueous lithium battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution. The non-aqueous lithium battery can be obtained by injecting the non-aqueous electrolyte solution between the negative electrode and the positive electrode (optionally with a separator).

[0051] The following examples are offered for illustrative purposes and are not intended to limit the scope of the invention.

[0052] In Examples 1 to 4, a modified horizontal UL-94 test was carried out. This modified horizontal UL-94 test is very similar to the known published horizontal UL-94 test. For example, see Otsuki, M. et al. "Flame-Retardant See “Additives for Lithium-Ion Batteries.” Lithium-Ion Batteries. Ed. M. Yoshio et al. New York, Springer, 2009, pp. 275-289. The modified UL-94 test was performed as follows. The cores were cut from round fiberglass cores, the cut edges were smoothed, and the core surface was cleaned of dust and particles. Prior to testing, the cores were dried at 120° C. for 20 hours. The length of the cores was 5±0.1 inches (12.7±0.25 cm). Each specimen to be tested was prepared in a 4 oz (120 mL) glass vial in the drybox by combining the desired amount of flame retardant and electrochemical additive (if present) with the desired amount of plain electrolyte solution. For example, 8 wt% of a brominated flame retardant, 2 wt% of an electrochemical additive, and 90 wt% of electrolyte solution were combined to form an electrolyte solution containing the flame retardant(s). The plain electrolyte solution, prior to combination with the flame retardant, was contained in a 4 oz (120 mL) glass vial and contained 1.2 M LiPF6 in ethylene carbonate / ethyl methyl carbonate (3:7 by weight). Each wick was immersed in the electrolyte solution for 30 minutes. Each test specimen was removed from the electrolyte solution, held above the electrolyte solution until it stopped dripping, and then placed in a 4 oz (120 mL) glass jar and capped to prevent evaporation of the electrolyte solution. The burner was ignited and adjusted to produce a blue flame 20±1 mm high. The test specimen was removed from the 4 ounce (120 mL) glass bottle and placed in a horizontal position on a metal support fixture with one end of the wick secured in place. If the exhaust fan was running, it was stopped for the test. The flame was directed at an angle of 45±2 degrees to the horizontal wick. For burners with a burner tube, one way to accomplish this was to tilt the central axis of the burner tube toward the end of the specimen at an angle of 45±2 degrees from the horizontal. The flame was applied to the free end of the specimen for 30±1 seconds without changing its position, and the burner was removed after 30±1 seconds or as soon as the burn front of the specimen reached the 1 inch (2.54 cm) position. If the test specimen continues to burn after the test flame is removed, the time until the flame is extinguished or the flame front (flame The time it took for the stick to move from the 1 inch (2.54 cm) mark to the 4 inch (10.16 cm) mark was recorded in seconds.

[0053] If the flame was extinguished when the burner was removed, the specimen was considered "non-flammable." If the flame was extinguished before reaching the 1 inch (2.54 cm) mark, the specimen was considered "flame-retardant." If the flame was extinguished before reaching the 4 inch (10.16 cm) mark, the specimen was considered "self-extinguishing."

[0054] Each modified horizontal UL-94 test result is the average of three runs.

[0055] Example 1 Several non-aqueous electrolyte solutions containing either tribromoethylene or tribromoneopentyl alcohol were prepared as described above and subjected to the modified UL-94 test described above. The results are summarized below in Table 1. As above, the reported values ​​are averages from three runs. [Table 1] Example 2

[0056] Several non-aqueous electrolyte solutions containing a mixture of brominated flame retardants were prepared as described above and subjected to the modified UL-94 test described above. The results are summarized below in Table 2. As above, the reported values ​​are the average of three runs. [Table 2]

[0057] Example 3 Several non-aqueous electrolyte solutions containing a mixture of flame retardants were prepared as described above and subjected to the modified UL-94 test described above. The results are summarized below in Table 3. As above, the reported values ​​are the average of three runs. [Table 3]

[0058] Example 4 Several non-aqueous electrolyte solutions containing brominated flame retardants were also tested in coin cells. Coin cells were assembled with the non-aqueous electrolyte solutions containing the desired amounts of flame retardants. The coin cells were then subjected to electrochemical cycling with a CCCV charge at C / 5 to 4.2 V with a current cutoff of C / 50 in the CV portion, and a CC discharge at C / 5 to 3.0 V.

[0059] One sample contained 1.2M LiPF6 in ethylene carbonate / ethyl methyl carbonate (3:7 by weight), a non-aqueous electrolyte solution without flame retardant. The remaining samples contained the desired amount of flame retardant in the electrolyte solution, and some solutions contained additives in addition to the flame retardant. The results are summarized in Table 4 below. The margin of error for the coulombic efficiency is about ±0.5% to about ±1.0%. The results reported in Table 4 are the average of multiple cells. "Multiple cells" typically means 2-3 cells. [Table 4]

[0060] Example 5 Further flammability testing of non-aqueous electrolyte solutions was performed at Sandia National Laboratories. This thermal abuse test was conducted to more closely resemble the conditions under which the electrolyte must be non-flammable under abuse conditions, specifically a battery venting in combination with an ignition source. Testing was performed by filling an 18650 size battery with approximately 5 mL of non-aqueous electrolyte solution, crimping the battery with a typical cell header assembly, and heating the battery with electrolyte at a fixed rate of 5°C / min using a spark-wire ignition source in a fixed position approximately 2 inches above the cell header. At approximately 200°C the battery began to vent, aerosolizing the hot electrolyte solution, which was then exposed to the spark-wire ignition source. Each sample was monitored for ignition and was considered a pass if it did not ignite, or a fail if it ignited.

[0061] One sample contained a non-aqueous electrolyte solution without flame retardant, 1.2M LiPF6 in ethylene carbonate / ethyl methyl carbonate (weight ratio 3:7). The remaining samples contained the desired amount of flame retardant in the electrolyte solution. The results are summarized in Table 5 below. [Table 5]

[0062] Further embodiments include, but are not limited to, the following:

[0063] A. A non-aqueous electrolyte solution for a lithium battery, comprising: a) a liquid electrolyte medium; b) a lithium-containing salt; and c) a flame retarding amount of a brominated flame retardant selected from tribromoethylene and tribromoneopentyl alcohol; The solution comprising:

[0064] B. The solution of A, wherein the amount of flame retardant is greater than 4 wt.%, based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0065] C. The solution of A, wherein the amount of flame retardant is greater than 6 wt.%, based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0066] D. The solution of A, wherein the amount of flame retardant is greater than 8 wt.%, based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0067] E. The solution of claim 1, wherein the amount of flame retardant is about 8 wt% to about 10 wt%, based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0068] F. The solution of A, wherein the amount of flame retardant is greater than 10 wt.%, based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0069] G. The solution of A, wherein the amount of flame retardant is greater than 10 wt.%, based on the total weight of the solution, and the brominated flame retardant is tribromoneopentyl alcohol.

[0070] H. The solution of A, wherein the amount of flame retardant is greater than 15 wt.%, based on the total weight of the solution.

[0071] I. The solution according to any one of A to D, wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and / or the lithium-containing salt is lithium hexafluorophosphate or lithium bis(oxalato)borate.

[0072] J. A non-aqueous lithium battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte solution according to any one of A to I.

[0073] K. A method for producing a non-aqueous electrolyte solution for a lithium battery, comprising: a) a liquid electrolyte medium; b) a lithium-containing salt; and c) a flame retarding amount of a brominated flame retardant selected from tribromoethylene and tribromoneopentyl alcohol; The method comprising combining components comprising:

[0074] L. The method of K, wherein the amount of flame retardant is greater than 4 wt.% based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0075] M. The method of claim K, wherein the amount of flame retardant is greater than 6 wt.% based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0076] N. The method of claim K, wherein the amount of flame retardant is greater than 8 wt.% based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0077] O. The method of claim K, wherein the amount of flame retardant is about 8 wt % to about 10 wt % based on the total weight of the solution, and the brominated flame retardant is tribromoethylene.

[0078] P. The method of claim K, wherein the amount of flame retardant is greater than 10 wt. % based on the total weight of the solution, and the brominated flame retardant is tribromoneopentyl alcohol.

[0079] Q. The method of K, wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and / or the lithium-containing salt is lithium hexafluorophosphate or lithium bis(oxalato)borate.

[0080] R. The method of any of K-Q, wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and / or the lithium-containing salt is lithium hexafluorophosphate or lithium bis(oxalato)borate.

[0081] Any component referred to by chemical name or formula anywhere in this specification or in this claim, whether referred to in the singular or plural, is identified as being present prior to contact with another substance (e.g., another component, solvent, etc.) referred to by chemical name or chemical type. It is immaterial what chemical change, transformation, and / or reaction (if any) occurs in the resulting mixture or solution, since such change, transformation, and / or reaction is a natural result from bringing together the specified components under the conditions invoked in accordance with this disclosure. Thus, the components are identified as ingredients that come together in connection with performing a desired operation or in forming a desired composition. Also, in the claims that follow, any reference to a substance, component, and / or ingredient in the present tense (such as "comprising," "being," etc.) is a reference to the substance, component, or ingredient as it existed immediately prior to first being contacted, blended, or mixed with one or more other substances, components, and / or ingredients in accordance with this disclosure. Thus, the fact that substances, components, or ingredients, when contacted, blended, or mixed in accordance with this disclosure and the ordinary skill of a chemist, may have lost their original identity due to intermediate chemical reaction or transformation is not of practical concern.

[0082] The present invention may comprise, consist of, or consist essentially of the materials and / or procedures described herein.

[0083] As used herein, the term "about" to modify the amount of an ingredient in a composition of the invention or used in a method of the invention refers to the variability of the numerical amount that may arise, for example, from typical measuring and liquid handling procedures used to make concentrates or use solutions in the real world, from inadvertent errors in such procedures, from differences in manufacture, source, or purity of ingredients used to make the composition or practice the method, and the like. The term about also encompasses amounts that vary due to differences in equilibrium conditions of the composition resulting from a particular initial mixture. Whether or not modified by the term "about," the claims include the equivalent of the amount.

[0084] Unless otherwise expressly indicated, the articles "a" or "an" as used herein are not intended, and should not be construed, as limiting the description or claim to the single element to which the article refers. Rather, as used herein, the articles "a" or "an" are intended to cover one or more such elements, unless the context expressly indicates otherwise.

[0085] This invention is susceptible to considerable variation in its practice, and therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.

Claims

1. A non-aqueous electrolyte solution for a lithium battery, the solution comprising: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) a flame retardant amount of A) tribromoethylene or tribromoneopentyl alcohol, the flame retardant amount being greater than 4 wt % for tribromoethylene and greater than 10 wt % for tribromoneopentyl alcohol, based on the total weight of the solution; or B) a) a flame retardant mixture of 1,2-dibromoethane and tribromoethylene in a weight ratio of 0.75:1 to 3:1; or b) a flame retardant mixture of tribromoethylene and 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine in a weight ratio of 0.75:1 to 2.25:1; The non-aqueous electrolyte solution comprises:

2. iii) is tribromoethylene or tribromoneopentyl alcohol, and the flame retardant amount is greater than 15 wt % based on the total weight of the solution; or It is a flame retardant mixture, and 1,2-dibromoethane and tribromoethylene, and the flame retardant amount is 6 wt % or more based on the total weight of the solution; or tribromoethylene and 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine, the flame retardant amount being 4 wt % or more based on the total weight of the solution; or The flame retardant mixture is 1,2-dibromoethane and tribromoethylene, and the amount of the flame retardant is 20 wt % or more based on the total weight of the solution. The solution of claim 1.

3. 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine, wherein the brominated flame retardant is tribromoethylene, the weight ratio of tribromoethylene:2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine is 0.75:1 to 2:1, and the flame retardant amount of flame retardant molecules is 4 wt% or more based on the total weight of the non-aqueous electrolyte solution.

4. 4. The solution of claim 1, wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and / or the lithium-containing salt is lithium hexafluorophosphate or lithium bis(oxalato)borate.

5. iii) is tribromoethylene or tribromoneopentyl alcohol, and the solution iv) at least one electrochemical additive selected from: a) unsaturated cyclic carbonates containing 3 to 6 carbon atoms; b) fluorine-containing saturated cyclic carbonates containing 3 to 5 carbon atoms and 1 to 4 fluorine atoms; c) tris(trihydrocarbylsilyl)phosphites containing 3 to 9 carbon atoms; d) trihydrocarbyl phosphates containing 3 to 12 carbon atoms; e) cyclic sultones containing 3 to 8 carbon atoms; f) saturated cyclic hydrocarbyl sulfites having 5- or 6-membered rings and containing 2 to 6 carbon atoms; g) saturated cyclic hydrocarbyl sulfates having 5- or 6-membered rings and containing 2 to 6 carbon atoms; h) cyclic dioxadithio polyoxide compounds having 6, 7, or 8 membered rings and containing 2 to 6 carbon atoms; i) another lithium-containing salt, and j) A mixture of two or more of the above 2. The solution of claim 1 further comprising:

6. The electrochemical additive is a) unsaturated cyclic carbonates containing 3 to 4 carbon atoms; b) fluorine-containing saturated cyclic carbonates containing 3 to 4 carbon atoms and 1 to 2 fluorine atoms; c) tris(trihydrocarbylsilyl)phosphites containing 3 to 6 carbon atoms; d) trihydrocarbyl phosphates containing 3 to 9 carbon atoms; e) cyclic sultones containing 3 to 4 carbon atoms; f) saturated cyclic hydrocarbyl sulfates having a 5-membered ring and containing 2 to 4 carbon atoms; g) saturated cyclic hydrocarbyl sulfates having a 5-membered ring and containing 2 to 4 carbon atoms; h) cyclic dioxadithio polyoxide compounds having a 6- or 7-membered ring and containing 2 to 4 carbon atoms; i) another lithium-containing salt, and j) A mixture of two or more of the above The solution according to claim 5 , wherein the solution is selected from the group consisting of

7. The electrochemical additive is a) 0.5 wt % to 12 wt % of an unsaturated cyclic carbonate, based on the total weight of the non-aqueous electrolyte solution; b) 0.5 wt % to 15 wt % of a fluorine-containing saturated cyclic carbonate based on the total weight of the non-aqueous electrolyte solution. c) 0.1 wt % to 5 wt % of tris(trihydrocarbylsilyl)phosphite, based on the total weight of the non-aqueous electrolyte solution; d) 0.5 wt % to 5 wt % of a trihydrocarbyl phosphate, based on the total weight of the non-aqueous electrolyte solution; e) 0.25 wt % to 5 wt % of a cyclic sultone based on the total weight of the non-aqueous electrolyte solution; f) 0.5 wt % to 5 wt % of a saturated cyclic hydrocarbyl sulfite, based on the total weight of the non-aqueous electrolyte solution; g) 0.25 wt % to 5 wt % of a saturated cyclic hydrocarbyl sulfate, based on the total weight of the non-aqueous electrolyte solution; h) 0.5 wt % to 5 wt % of a cyclic dioxadithio polyoxide compound based on the total weight of the non-aqueous electrolyte solution; i) 0.5 wt % to 5 wt % of another lithium-containing salt, based on the total weight of the non-aqueous electrolyte solution; and j) A mixture of two or more of the above The solution according to claim 5 or 6, selected from:

8. The electrochemical additive is a saturated cyclic hydrocarbyl sulfate, a cyclic sultone, a tris(trihydrocarbylsilyl)phosphite, or another lithium-containing salt; or 1 wt % to 4 wt % of a saturated cyclic hydrocarbyl sulfate, 0.5 wt % to 4 wt % of a cyclic sultone, 0.2 wt % to 3 wt % of a tris(trihydrocarbylsilyl)phosphite, or 1 wt % to 4 wt % of another lithium-containing salt, each based on the total weight of the non-aqueous electrolyte solution; or vinylene carbonate, 1,3,2-dioxathiolane 2,2-dioxide, 1,3-propene sultone, 1,3-propane sultone, tris(trimethylsilyl)phosphite, or lithium bis(oxalato)borate; The solution according to any one of claims 5 to 7.

9. 10. The solution of claim 8, wherein each electrochemical additive is not used with other electrochemical additives.

10. 8. The solution of any one of claims 5 to 7, wherein the electrochemical additive is selected from vinylene carbonate, 4-fluoroethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1-propane-1,3-sultone, 1-propene-1,3-sultone, 1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium bis(oxalato)borate, and mixtures of any two or more thereof.

11. The electrochemical additive is 0.5 wt % to 3 wt % of vinylene carbonate, based on the total weight of the non-aqueous electrolyte solution; 8 wt % to 11 wt % of vinylene carbonate, based on the total weight of the non-aqueous electrolyte solution; 0.5 wt % to 15 wt % of 4-fluoroethylene carbonate, based on the total weight of the non-aqueous electrolyte solution; 0.2 wt % to 3 wt % of tris(trimethylsilyl)phosphite, based on the total weight of the non-aqueous electrolyte solution; 1 wt % to 5 wt % of triallyl phosphate, based on the total weight of the non-aqueous electrolyte solution; 0.5 wt % to 4 wt % of 1,3-propane sultone or 1,3-propene sultone, based on the total weight of the non-aqueous electrolyte solution; 1 wt % to 4 wt % of 1,3,2-dioxathiolane 2-oxide, based on the total weight of the non-aqueous electrolyte solution; 1 wt % to 4 wt % of 1,3,2-dioxathiolane 2,2-dioxide, based on the total weight of the non-aqueous electrolyte solution; 1 wt % to 4 wt % of 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, based on the total weight of the non-aqueous electrolyte solution; 1 wt % to 4 wt % of lithium bis(oxalato)borate, based on the total weight of the non-aqueous electrolyte solution; and A mixture of any two or more of these The solution of claim 10, wherein the solution is selected from the group consisting of:

12. The electrochemical additive is vinylene carbonate, 1-propane-1,3-sultone, 1-propene-1,3-sultone, 1,3,2-dioxathiolane 2,2-dioxide, tris(trimethylsilyl)phosphite, and lithium bis(oxalato)borate; or 0.5 wt % to 4 wt % of 1-propane-1,3-sultone, 0.5 wt % to 4 wt % of 1-propene-1,3-sultone, 1 wt % to 4 wt % of 1,3,2-dioxathiolane 2,2-dioxide, and 1 wt % to 4 wt % of lithium bis(oxalato)borate, each based on the total weight of the non-aqueous electrolyte solution; 12. The solution according to claim 10 or 11.

13. 13. The solution of claim 12, wherein each electrochemical additive is not used with other electrochemical additives.

14. A non-aqueous lithium battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte solution according to any one of claims 1 to 13.

15. 1. A method for making a non-aqueous electrolyte solution for a lithium battery, the method comprising: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) a flame retardant amount of A) tribromoethylene or tribromoneopentyl alcohol, the flame retardant amount being greater than 4 wt % for tribromoethylene and greater than 10 wt % for tribromoneopentyl alcohol, based on the total weight of the solution; or B) a) a flame retardant mixture of 1,2-dibromoethane and tribromoethylene in a weight ratio of 0.75:1 to 3:1; or b) a flame retardant mixture of tribromoethylene and 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine in a weight ratio of 0.75:1 to 2.25:1; The method comprising combining components comprising:

16. iii) is tribromoethylene or tribromoneopentyl alcohol, said component being iv) at least one electrochemical additive selected from: a) unsaturated cyclic carbonates containing 3 to 6 carbon atoms; b) fluorine-containing saturated cyclic carbonates containing 3 to 5 carbon atoms and 1 to 4 fluorine atoms; c) tris(trihydrocarbylsilyl)phosphites containing 3 to 9 carbon atoms; d) trihydrocarbyl phosphates containing 3 to 12 carbon atoms; e) cyclic sultones containing 3 to 8 carbon atoms; f) saturated cyclic hydrocarbyl sulfites having 5- or 6-membered rings and containing 2 to 6 carbon atoms; g) saturated cyclic hydrocarbyl sulfates having 5- or 6-membered rings and containing 2 to 6 carbon atoms; h) cyclic dioxadithio polyoxide compounds having 6, 7, or 8 membered rings and containing 2 to 6 carbon atoms; i) another lithium-containing salt, and j) A mixture of two or more of the above The method of claim 15 further comprising:

17. 17. The method of claim 16, wherein the electrochemical additive is selected from vinylene carbonate, 4-fluoroethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1-propane-1,3-sultone, 1-propene-1,3-sultone, 1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium bis(oxalato)borate, and mixtures of any two or more thereof.

18. iii) is tribromoethylene or tribromoneopentyl alcohol, and the flame retardant amount is greater than 15 wt % based on the total weight of the solution; or a flame retardant mixture, comprising 1,2-dibromoethane and tribromoethylene, the amount of said flame retardant being 6 wt % or more based on the total weight of said solution; or tribromoethylene and 2-phenoxy-2,4,4,6,6-pentafluoro-1,3,5,2λ5,4λ5,6λ5 triazatriphosphinine, the flame retardant amount being 4 wt % or more based on the total weight of the solution; or 1,2-dibromoethane and tribromoethylene, and the flame retardant amount is 20 wt % or more based on the total weight of the solution; The method of claim 15.

19. 17. The method of claim 15 or 16, wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and / or the lithium-containing salt is lithium hexafluorophosphate or lithium bis(oxalato)borate.

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