Flame Retardants For Battery Electrolytes

Abstract

This invention provides nonaqueous electrolyte solutions for lithium batteries. The nonaqueous electrolyte solutions comprise a liquid electrolyte medium; a lithium-containing salt; and at least one oxygen-containing brominated flame retardant.

Claims

1. A nonaqueous electrolyte solution for a lithium battery, which solution comprises i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one oxygen-containing brominated flame retardant selected from A) a brominated noncyclic carbonate in which the carbon-carbon bonds are saturated, B) a brominated cyclic carbonate having a carbonate ring in which the carbon-carbon bonds are saturated, with the proviso that the brominated cyclic carbonate is not 4-bromomethyl ethylene carbonate, and C) at least one oxygen-containing brominated flame retardant selected from the group consisting of 2-bromoethyl methyl carbonate, 2,2-dibromoethyl methyl carbonate, 2,2,2-tribromoethyl methyl carbonate, bis(2-bromoethyl) carbonate, 4-bromo-1,3-dioxolan-2-one, 4,5-dibromo-1,3-dioxolan-2-one, 4,4,5-tribromo-1,3-dioxolan-2-one, 4,4-bis(bromomethyl)-1,3-dioxolan-2-one, 4,5-bis(bromomethyl)-1,3-dioxolan-2-one, 4-(2-bromoethenyl)-1,3-dioxolan-2-one, 5-(bromomethyl)-5-methyl-1,3-dioxan-2-one, and 5,5-bis(bromomethyl)-1,3-dioxan-2-one.

2. A solution as in claim 1 wherein the brominated flame retardant is A) or B), and wherein the oxygen-containing brominated flame retardant has about three to about ten carbon atoms, one to about five bromine atoms, and/or a bromine content of about 35 wt % or more relative to the total weight of the oxygen-containing brominated flame retardant or the oxygen-containing brominated flame retardant is a brominated noncyclic carbonate which has about four to about eight carbon atoms and one to about four bromine atoms; or a brominated cyclic carbonate which has about three to about eight carbon atoms, one to about four bromine atoms, and a bromine content of about 35 wt % or more relative to the total weight of the oxygen-containing brominated flame retardant.

3. (canceled)

4. A solution as in claim 1 wherein the brominated flame retardant is A) or B), and wherein the oxygen-containing brominated flame retardant is a brominated noncyclic carbonate; or a brominated cyclic carbonate containing two or more bromine atoms wherein all of the bromine atoms are in one or more hydrocarbyl groups bound to the carbonate ring, or all of the bromine atoms are bound to carbon atoms of the carbonate ring.

5. A solution as in claim 4 wherein the oxygen-containing brominated flame retardant is a brominated noncyclic carbonate having hydrocarbyl groups which are selected from methyl and ethyl groups; or a brominated cyclic carbonate containing two or more bromine atoms and having two or more hydrocarbyl groups bound to the carbonate ring, wherein the bromine atoms are in different hydrocarbyl groups.

6. A solution of claim 1 wherein the brominated flame retardant is A) or B), and wherein the oxygen-containing brominated flame retardant is a brominated noncyclic carbonate in which one hydrocarbyl group is a methyl group; or a brominated cyclic carbonate having two or more hydrocarbyl groups bound to the carbonate ring, which hydrocarbyl groups are methyl groups; or a brominated cyclic carbonate which has a 5-membered or 6-membered ring, and optionally has about 3 to about 8 carbon atoms, one to about five bromine atoms, and/or a bromine content of about 35 wt % or more relative to the total weight of the oxygen-containing brominated flame retardant.

7-8. (canceled)

9. A solution of claim 1 wherein the oxygen-containing brominated flame retardant is 4-(2-bromoethenyl)-1,3-dioxolan-2-one, 5-(bromomethyl)-5-methyl-1,3-dioxan-2-one, or 5,5-bis(bromomethyl)-1,3-dioxan-2-one.

10. A solution as in claim 1 wherein the brominated flame retardant of A) or B) has a boiling point of about 95° C. or higher, or wherein the brominated flame retardant of A) or B) has a boiling point in the range of about 75° C. to about 450° C.

11. (canceled)

12. A solution as in claim 1 wherein the oxygen-containing brominated flame retardant is in an amount of about 10 wt % or more bromine relative to the total weight of the solution, and/or wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and/or wherein the lithium-containing salt is lithium hexafluorophosphate, lithium di(fluoro)(oxalato)borate, or lithium bis(oxalato)borate.

13. (canceled)

14. A solution as in claim 1 further comprising at least one electrochemical additive selected from: a) unsaturated cyclic carbonates containing three to about six carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about five carbon atoms and one to about four fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about nine carbon atoms, d) trihydrocarbyl phosphates containing three to about twelve carbon atoms, e) cyclic sultones containing three to about eight carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered or 6-membered ring and containing two to about six carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered or 6-membered ring and containing two to about six carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered, 7-membered, or 8-membered ring and containing two to about six carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing.

15. A solution as in claim 14 wherein 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.

16. A solution as in claim 14 wherein the electrochemical additive is selected from: a) an unsaturated cyclic carbonate in an amount of about 0.5 wt % to about 12 wt %, relative to the total weight of the nonaqueous electrolyte solution, b) a fluorine-containing saturated cyclic carbonate in an amount of about 0.5 wt % to about 8 wt %, relative to the total weight of the nonaqueous electrolyte solution, c) a tris(trihydrocarbylsilyl) phosphite in an amount of about 0.1 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, d) a trihydrocarbyl phosphate in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, e) a cyclic sultone in an amount of about 0.25 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, f) a saturated cyclic hydrocarbyl sulfite in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, g) a saturated cyclic hydrocarbyl sulfate in an amount of about 0.25 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, h) a cyclic dioxadithio polyoxide compound in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, i) another lithium-containing salt in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, and j) mixtures of any two or more of the foregoing.

17. A solution as in claim 14 wherein the electrochemical additive is a saturated cyclic hydrocarbyl sulfate, a cyclic sultone, a tris(trihydrocarbylsilyl) phosphite, or another lithium-containing salt.

18. A solution as in claim 14 wherein the electrochemical additive is an unsaturated cyclic carbonate in an amount of about 0.5 wt % to about 3 wt %, a saturated cyclic hydrocarbyl sulfate in an amount of about 1 wt % to about 4 wt %, a cyclic sultone in an amount of about 0.5 wt % to about 4 wt %, a tris(trihydrocarbylsilyl) phosphite in an amount of about 0.2 wt % to about 3 wt %, or another lithium-containing salt in an amount of about 1 wt % to about 4 wt %, each relative to the total weight of the nonaqueous electrolyte solution; or vinylene carbonate, 1,3,2-dioxathiolane 2,2-dioxide, 1,3-propene sultone, 1,3-propane sultone, tris(trimethylsilyl)phosphite, lithium di(fluoro)(oxalato)borate, or lithium bis(oxalato)borate.

19. (canceled)

20. A solution as in claim 18 wherein each electrochemical additive is not used with other electrochemical additives.

21. A solution as in claim 14 wherein the electrochemical additive is selected from vinylene carbonate, 4-fluoro-ethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium di(fluoro)(oxalato)borate, lithium bis(oxalato)borate, and mixtures of any two or more of these.

22. A solution as in claim 21 wherein the electrochemical additive is selected from: vinylene carbonate in an amount of about 0.5 wt % to about 3 wt %, relative to the total weight of the nonaqueous electrolyte solution; vinylene carbonate in an amount of about 8 wt % to about 11 wt %, relative to the total weight of the nonaqueous electrolyte solution; 4-fluoro-ethylene carbonate in an amount of about 1.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution; tris(trimethylsilyl)phosphite in an amount of about 0.2 wt % to about 3 wt %, relative to the total weight of the nonaqueous electrolyte solution; triallyl phosphate in an amount of about 1 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3-propane sultone or 1,3-propene sultone in an amount of about 0.5 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3-propane sultone in an amount of about 1.5 wt % to about 10 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3,2-dioxathiolane, 2-oxide in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3,2-dioxathiolane 2,2-dioxide in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; lithium di(fluoro)(oxalato)borate in an amount of about 1 wt % to about 10 wt %, relative to the total weight of the nonaqueous electrolyte solution; lithium di(fluoro)(oxalato)borate in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; lithium bis(oxalato)borate in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; and mixtures of any two or more of these.

23. A solution as in claim 21 wherein the electrochemical additive is selected from vinylene carbonate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane 2,2-dioxide, tris(trimethylsilyl)phosphite, lithium di(fluoro)(oxalato)borate, and lithium bis(oxalato)borate; or selected from vinylene carbonate in an amount of about 0.5 wt % to about 3 wt %, 1,3-propane sultone in an amount of about 0.5 wt % to about 4 wt %, 1,3-propane sultone in an amount of about 1.5 wt % to about 10 wt %, 1,3-propene sultone in an amount of about 0.5 wt % to about 4 wt %, 1,3,2-dioxathiolane 2,2-dioxide, in an amount of about 1 wt % to about 4 wt %, lithium di(fluoro)(oxalato)borate in an amount of about 1 wt % to about 10 wt %, lithium di(fluoro)(oxalato)borate in an amount of about 1 wt % to about 4 wt %, and lithium bis(oxalato)borate in an amount of about 1 wt % to about 4 wt %, each relative to the total weight of the nonaqueous electrolyte solution.

24. (canceled)

25. A solution as in claim 23 wherein the flame retardant comprises 4-(2-bromoethenyl)-1,3-dioxolan-2-one.

26. A solution as in claim 23 wherein each electrochemical additive is not used with other electrochemical additives.

27. A nonaqueous lithium battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte solution as in claim 1.

28-32. (canceled)

33. A process for producing a nonaqueous electrolyte solution for a lithium battery, which process comprises combining components comprising: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) at least one oxygen-containing brominated flame retardant selected from A) a brominated noncyclic carbonate in which the carbon-carbon bonds are saturated, B) a brominated cyclic carbonate having a carbonate ring in which the carbon-carbon bonds are saturated, with the proviso that the brominated cyclic carbonate is not 4-bromomethyl ethylene carbonate, and C) at least one oxygen-containing brominated flame retardant selected from the group consisting of 2-bromoethyl methyl carbonate, 2,2-dibromoethyl methyl carbonate, 2,2,2-tribromoethyl methyl carbonate, bis(2-bromoethyl) carbonate, 4-bromo-1,3-dioxolan-2-one, 4,5-dibromo-1,3-dioxolan-2-one, 4,4,5-tribromo-1,3-dioxolan-2-one, 4,4-bis(bromomethyl)-1,3-dioxolan-2-one, 4,5-bis(bromomethyl)-1,3-dioxolan-2-one, 4-(2-bromoethenyl)-1,3-dioxolan-2-one, 5-(bromomethyl)-5-methyl-1,3-dioxan-2-one, and 5,5-bis(bromomethyl)-1,3-dioxan-2-one.

34. A process as in claim 33 wherein the components further comprise at least one electrochemical additive selected from: a) unsaturated cyclic carbonates containing three to about six carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about five carbon atoms and one to about four fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about nine carbon atoms, d) trihydrocarbyl phosphates containing three to about twelve carbon atoms, e) cyclic sultones containing three to about eight carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered or 6-membered ring and containing two to about six carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered or 6-membered ring and containing two to about six carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered, 7-membered, or 8-membered ring and containing two to about six carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing.

35. (canceled)

36. A process as in claim 35 wherein the brominated flame retardant is C), and wherein the components further comprise at least one electrochemical additive selected from vinylene carbonate, 4-fluoro-ethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium di(fluoro)(oxalato)borate, lithium bis(oxalato)borate, and mixtures of any two or more of these.

37. 4-(2-Bromoethenyl)-1,3-dioxolan-2-one.

Description

EXAMPLE 1

[0070] Nonaqueous electrolyte solutions containing 4-(2-bromoethenyl)-1,3-dioxolan-2-one, prepared as described above, were subjected to the modified UL-94 test described above. Results are summarized in Table 1 below; as noted above, the reported numbers are an average value from three runs.

TABLE-US-00001 TABLE 1 Flame retardant Bromine Time to Flame retardant in soln. in soln. Result exting. 4-(2-bromoethenyl)-1,3-dioxolan-2-one 25 wt % 10.38 wt % flame retardant 19 s

EXAMPLE 2

[0071] Tests of some nonaqueous electrolyte solutions containing brominated flame retardants in coin cells were carried out. Coin cells were assembled using nonaqueous electrolyte solutions containing the desired amount of flame retardant. 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.

[0072] One sample was a nonaqueous electrolyte solution without a flame retardant, and contained 1.2 M LiPF.sub.6 in ethylene carbonate/ethyl methyl carbonate (wt ratio 3:7). The rest of the samples contained the desired amount of flame retardant in the electrolyte solution. Results are summarized in Tables 2A and 2B below; the error range in the Coulombic efficiencies is about 0.5% to about +1,0%. Results reported in Table 2A are averages from multiple cells except where noted; “multiple cells” usually means two or three cells. Results reported in Table 2B are from the single best-performing cell.

TABLE-US-00002 TABLE 2A Coulombic Flame efficiency retardant Bromine Additive 1st 10th Chemical Name in soln. in soln. in soln. cycle cycle Electrolyte soln..sup.1 0 0 0 81.8% 99.6% 4,5 -dibromo-1,3-dioxolan-2-one 8 wt % 5.2 wt % 0   0% 29.5% 5,5-bis(bromomethyl)-1,3-dioxan-2-one 8 wt % 4.4 wt % 0 54.5% 94.1% 4,5-bis(bromomethyl)-1,3-dioxolan-2-one 8 wt % 4.4 wt % 0 12.5% 65.2% 4-(2-bromoethenyl)-1,3-dioxolan-2-one.sup.2 8 wt % 3.32 wt % 0 79.0% 99.6% 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 10.38 wt % 4 wt % 82.2% 98.5% 1,3-propane sultone.sup.2,3 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 10.38 wt % 6 wt % 81.7% 98.7% 1,3-propane sultone.sup.2,3 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 10.38 wt % 4 wt % 81.0% 99.6% lithium difluoro(oxalato)borate.sup.2,3 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 10.38 wt % 6 wt % 81.7% 98.7% lithium difluoro(oxalato)borate.sup.2,3 .sup.1Comparative run. .sup.2Data is from single best-performing cell. .sup.3Additional LiPF.sub.6 salt was added to the 4-(2-bromoethenyl)-1,3-dioxolan-2-one flame retardant in an effort to increase the total electrolyte conductivity. The total effective concentration of LiPF.sub.6 in the flame retardant-containing electrolyte was 1.1M prior to the addition of the additive.

[0073] Some flame retardants were tested in coin cells to 100 cycles; results are reported in Table 2B below. Data for each flame retardant below is reported from the single best-performing cell.

TABLE-US-00003 TABLE 2B Coulombic Capacity Flame efficiency fade retardant Additive 2nd 100th 2nd to Chemical name in soln. in soln. cycle cycle 100th cycle Electrolyte soln..sup.1 0 0 99.8% 100.3% 3.5% 4-(2-bromoethenyl)-1,3-dioxolan-2-one.sup.2 25 wt % 0 98.7% 99.9% 23.4% 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 2 wt % 88.0% 99.9% 11.4% 1,3-propane sultone.sup.2 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 2 wt % 99.2% 100.0% 17.6% vinylene carbonate.sup.2 4-(2-bromoethenyl)-1,3-dioxolan-2-one + 25 wt % 2 wt % 99.0% 100.0% 12.0% lithium difluoro(oxalato)borate.sup.2 .sup.1Comparative run. .sup.2Additional LiPF.sub.6 salt was added to the 4-(2-bromoethenyl)-1,3-dioxolan-2-one flame retardant in an effort to increase the total electrolyte conductivity. The total effective concentration of LiPF.sub.6 in the flame retardant-containing electrolyte was 1.1M prior to the addition of the additive.

EXAMPLE 3

Synthesis of 4-(2-bromoethenyl)-1,3-dioxolan-2-one

[0074] Dichloromethane (100 mL) and 4-ethenyl-1,3-dioxolan-2-one (22.8 g, 0.2 mol) were introduced to a 250-mL round bottom flask and then magnetically stirred in an ice cold water bath. To this mixture Br.sub.2 (32 g, 0.2 mol) was added slowly using a peristaltic pump. After all of the Br.sub.2 had been added, the reaction mixture was stirred for 2 hours while allowing the reaction mixture to reach room temperature. The reaction flask was then was placed in an ice cold water bath, and triethylamine (22.3 g, 0.22 mol) was added to the flask dropwise from an addition funnel. After all of the triethylamine had been added, the reaction mixture was stirred for 4 hours while allowing the reaction mixture to reach room temperature. The mixture was filtered to remove the solid that had formed, and the residual solution was collected in a 250-mL round flask. The solvent was removed from residual solution in the round flask, and then the residual liquid in the round flask was passed through a silica gel column, and purified by vacuum distillation to obtain 4-(2-bromoethenyl)-1,3-dioxolan-2-one (19.6 g; 50.8% yield).

[0075] 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.

[0076] The invention may comprise, consist, or consist essentially of the materials and/or procedures recited herein.

[0077] As used herein, the term “about” modifying the quantity of an ingredient in the compositions of the invention or employed in the methods of the invention refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods; and the like. The term about also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term “about”, the claims include equivalents to the quantities.

[0078] Except as may be expressly otherwise indicated, the article “a” or “an” if and as used herein is not intended to limit, and should not be construed as limiting, the description or a claim to a single element to which the article refers. Rather, the article “a” or “an” if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise.

[0079] This invention is susceptible to considerable variation in its practice. Therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.