Electrolyte formulations for optimal performance in Si-containing lithium ion batteries

1. An energy storage device comprising:

a first electrode and a second electrode, wherein one or both of the first electrode and the second electrode is a Si-based electrode;

a separator between the first electrode and the second electrode; and

an electrolyte composition;

wherein said electrolyte composition comprises two or more lithium salts,

10-50 wt % of one or more fluorinated solvents,

50-90 wt % of one or more non-fluorinated solvents, and

one or more additives comprising a total of between 0.25-1.5 wt % of the total electrolyte composition; and

wherein said one or more additives are selected from the group consisting of PES (prop-1-ene-1,3-sultone), TMSP (tris(trimethylsilyl)phosphite), TMS (trimethylene sulfate), TMSO (3-trimethylsilyl-2-oxazolidinone), and PMS (propargyl methanesulfonate);

said Si-based electrode is a silicon dominant electrode where the amount of silicon in the active material comprises 70% or more by weight; and

said one or more fluorinated solvents comprises fluorobenzene (FB).

2. The energy storage device of claim 1 , wherein said two or more lithium salts have a total molarity between 1 and 2.

3. The energy storage device of claim 2 , wherein said two or more lithium A salts have a total molarity between 1.2 and 1.6 M.

4. The energy storage device of claim 1 , wherein two lithium salts are included in said electrolyte composition.

5. The energy storage device of claim 4 , wherein said two lithium salts are selected from the group consisting of LiBF 4 , LiFSI, LiTFSI and LiPF 6 .

6. The energy storage device of claim 5 , wherein said two lithium salts are LiTFSI and LiPF 6 .

7. The energy storage device of claim 5 , wherein said two lithium salts are LiFSI and LiPF 6 .

8. The energy storage device of claim 1 , wherein three lithium salts are included in said electrolyte composition.

9. The energy storage device of claim 1 , wherein said two or more lithium salts are selected from the group consisting of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate monohydrate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalate)borate (LiDFOB), lithium triflate (LiCF 3 SO 3 ), lithium tetrafluorooxalato phosphate (LTFOP), lithium difluorophosphate (LiPO 2 F 2 ), lithium pentafluoroethyltrifluoroborate (LiFAB), and lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI), lithium bis(2-fluoromalonato)borate (LiBFMB), lithium 4-pyridyl trimethyl borate (LPTB), lithium 2-fluorophenol trimethyl borate (LFPTB), lithium catechol dimethyl borate (LiCDMB), and lithium tetrafluorooxalatophosphate (LiFOP).

10. The energy storage device of claim 1 , wherein said FB is present in the electrolyte composition at between 10 and 20 percent by weight.

11. The energy storage device of claim 1 , wherein said one or more non-fluorinated solvents are selected from the group consisting of one or more of EC (ethylene carbonate), PC (propylene carbonate), EMC (ethyl methyl carbonate), DMC (dimethyl carbonate), DEC (diethyl carbonate), GBL (gamma butyrolactone), MA (methyl acetate), EA (ethyl acetate), t-BC (trans-butylene carbonate), PMC (propyl methyl carbonate), DME (dimethoxyethane), EME (ethoxymethoxyethane), methyl propanoate and DEE (diethoxyethane).

12. The energy storage device of claim 11 , wherein said one or more non-fluorinated solvents comprises EMC.

13. The energy storage device of claim 11 , wherein said EMC is present in the electrolyte composition in an amount of 70-90% by weight.

14. The energy storage device of claim 1 , wherein said silicon in the active material comprises silicon particles.

15. The energy storage device of claim 1 , wherein said silicon particles are substantially silicon or a silicon alloy.

16. The energy storage device of claim 1 , wherein said silicon in the active material comprises silicon as the primary constituent along with one or more other elements.

17. The energy storage device of claim 1 , wherein two fluorinated solvents are included in said electrolyte composition.

18. The energy storage device of claim 2 , wherein the second fluorinated solvent is selected from the group consisting of FEC (fluoroethylene carbonate), F2EC (difluoroethylene carbonate), TTE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether), HFPM (1,1,1,3,3,3-hexafluoroisopropyl methyl ether), PTM (Phenyl trifluoromethane sulfonate), NOB (N,O-bis(trimethylsilyl)-trifluoroacetamide), FEMC (2-fluoroethyl methyl carbonate), FDMC (fluoromethyl methyl carbonate), FPC (4-fluoromethyl-1,3-dioxolan-2-one), F3EMC (methyl 2,2,2-trifluoroethyl carbonate), 1,1,2,2-Tetrafluoro-3-(1,1,2,2-tetrafluoroethoxy)-propane (TFTFEP), methyl nanofluorobutyl ether (MFE), ethyl nanofluorobutyl ether (EFE), 2-trifluoromethyl-3-methoxyperfluoropentane (TMMP), 2-(trifluoro-2-fluoro-3-difluoropropoxy)-3-difluoro-4-fluoro-5-trifluoropentane (TPTP), 2,2-bis(trifluoromethyl)-1,3-dioxolane, 2,2-dimethyl-4,5-difluoro-1,3-dioxolane, 2,2-dimethyl-4,4,5,5-tetrafluoro-1,3-dioxolane, 2-fluoroethoxymethoxyethane (FEME), 2,2-difluoroethoxymethoxyethane (DFEME), methoxy-2,2,2-trifluoroethoxyethane (TFEME), ethoxy-2-fluoroethoxyethane (EFEE), 2,2-difluoroethoxyethoxyethane (EDFEE), and ethoxy-2,2,2-trifluoroethoxyethane (ETFEE).

19. The energy storage device of claim 18 , wherein said second fluorinated solvent comprises fluoroethylene carbonate (FEC).

20. The energy storage device of claim 19 , wherein said FEC is present in the composition at between 10 and 30 percent by weight.