Electrolyte suitable for use in a lithium ion cell or battery
Electrolyte suitable for use in a lithium ion cell or battery. According to one embodiment, the electrolyte includes a fluorinated lithium ion salt and a solvent system that solvates lithium ions and that yields a high dielectric constant, a low viscosity and a high flashpoint. In one embodiment, the solvent system includes a mixture of an aprotic lithium ion solvating solvent and an aprotic fluorinated solvent.
1. A liquid electrolyte suitable for use in a lithium ion cell or battery, said liquid electrolyte comprising:
(a) a lithium salt; and
(b) a solvent system, said solvent system comprising
(i) a first aprotic solvent, said first aprotic solvent being a lithium ion solvating solvent; and
(ii) a second aprotic solvent, said second aprotic solvent being a fluorinated solvent, wherein said second aprotic solvent is at least a partially fluorinated ring structure containing and opposite to an —S(O) n group, wherein n=1 and wherein the S atom of said —S(O) n group is a member of said partially fluorinated ring structure.
2. The liquid electrolyte as claimed in claim 1 wherein said lithium salt is a fluorinated lithium salt.
3. The liquid electrolyte as claimed in claim 2 wherein said fluorinated lithium salt is selected from the group consisting of LiBF 4 , LiAsF 6 and LiPF 6 .
4. The liquid electrolyte as claimed in claim 1 wherein said first aprotic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, and butylene carbonate.
5. The liquid electrolyte as claimed in claim 1 wherein said second aprotic solvent is a fluorinated solvent having a molecular dipole moment in excess of 4 Debye.
6. The liquid electrolyte as claimed in claim 1 wherein the second aprotic solvent constitutes about 20-60% of said solvent system.
7. The liquid electrolyte as claimed in claim 1 wherein said solvent system further comprises at least one fluorinated hydrocarbon liquid.
8. The liquid electrolyte as claimed in claim 7 wherein said fluorinated hydrocarbon liquid is selected from the group consisting of 2,3-dihydrodecafluoropentane; 1,1,1-trifluoropentanedione; trifluoroethyl acetate; and 1,2-hexafluoropentane-3,4-dione.
9. An electrochemical cell comprising the liquid electrolyte of claim 1 , an anode, a cathode and a separator, the anode, the cathode and the separator being operatively associated with the liquid electrolyte, wherein the electrochemical cell is a lithium ion cell or battery.
10. A liquid electrolyte suitable for use in a lithium ion cell or battery, said liquid electrolyte comprising:
(a) a lithium salt; and
(b) a solvent system, said solvent system comprising
(i) first aprotic solvent, said first aprotic solvent being a lithium ion solvating solvent; and
(ii) a second aprotic solvent, said second aprotic solvent being a fluorinated solvent, wherein said second aprotic solvent is a compound of the general formula
wherein n=1; R 1 ═H or F; R 2 ═H or F; R 3 ═H or F; and R 4 ═H or F, with at least one of R 1 , R 2 , R 3 and R 4 being F.
11. The liquid electrolyte as claimed in claim 10 wherein at least one of R 2 and R 3 is F.