Fluoro-substituted ethers and compositions
Described herein are fluoro-substituted ethers of Formula (I): wherein R 1 is a fluoro-substituted C 2 -C 6 alkyl group; R 2 is a C 2 -C 6 alkyl group or a fluoro-substituted C 2 -C 6 alkyl group; each R 3 independently is H, F, methyl, or fluoro-substituted methyl; and n is 0, 1, 2, 3, or 4. The fluoro-substituted ether compounds are useful as solvents for lithium containing electrolytes in lithium batteries, particularly lithium-sulfur batteries.
1. A lithium-sulfur battery comprising a positive electrode, a negative electrode, and an electrolyte therebetween; wherein the positive electrode comprises sulfur, the negative electrode comprises lithium, and the electrolyte comprises a lithium salt dissolved in a solvent comprising one or more fluoro-substituted ether compound selected from the group consisting of:
1,1,1,11,11,11-hexafluoro-3,6,9-trioxaundecane,
1,1,1,14,14,14-hexafluoro-3,6,9,12-tetraoxatetradecane,
1,1,1,17,17,17-hexafluoro-3,6,9,12,15-pentaoxaheptadecane,
and 1,1,1,2,2,12,12,13,13,13-decafluoro-4,7,10-trioxatridecane.
2. The lithium-sulfur battery of claim 1 , wherein the solvent further comprises a co-solvent selected from one or more of an ether, a carbonate ester, a nitrile, a sulfoxide, and a sulfone.
3. The lithium-sulfur battery of claim 2 , wherein the co-solvent comprises one or more ether selected from dioxolane, tetrahydrofuran, dimethoxyethane, diglyme, triglyme, and tetraglyme.
4. The lithium-sulfur battery of claim 2 , wherein the co-solvent comprises one or more carbonate ester selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate.
5. The lithium-sulfur battery of claim 2 , wherein the co-solvent and the fluoro-substituted ether compound are present in the solvent mixture in a respective volume ratio in the range of about 1:9 to about 9:1.
6. The lithium-sulfur battery of claim 1 , wherein the lithium salt comprises one or more of lithium bis(trifluoromethane)sulfonimidate (LiTFSI), lithium 2-trifluoromethyl-4,5-dicyanoimidazolate (LiTDI), lithium 4,5-dicyano-1,2,3-triazolate (LiTDI), lithium trifluoromethanesulfonate (LiTf), lithium perchlorate (LiClO 4 ), lithium bis(oxalato)b orate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium thiocyanate (LiSCN), lithium bis(fluorosulfonyl)imidate (LIFSI), lithium bis(pentafluoroethylsulfonyl)imidate (LBETI), lithium tetracyanoborate (LiB(CN) 4 ), and lithium nitrate.
7. The lithium-sulfur battery of claim 1 , wherein the lithium salt comprises lithium bis(trifluoromethane)sulfonimidate.
8. The lithium-sulfur battery of claim 1 , wherein the lithium salt is present in the solvent at a concentration in the range of about 0.1 to about 1.2 molar.
9. The lithium-sulfur battery of claim 1 , wherein the positive electrode comprises particles of sulfur and particles of carbon held together with a binder.
10. The lithium-sulfur battery of claim 9 , wherein the particles of carbon comprise carbon black.
11. The lithium-sulfur battery of claim 9 , wherein the negative electrode comprises lithium metal.
12. The lithium-sulfur battery of claim 1 , wherein the positive electrode comprises a mixture of about 60 wt % of sulfur particles, 30 wt % of carbon black particles, and 20 wt % of poly(vinylidene difluoride) (PVDF) binder.
13. The lithium-sulfur battery of claim 12 , wherein the negative electrode comprises lithium metal.