Described herein are: An electrolyte composition comprising a) a fluorinated solvent for an electrolyte salt; b) an oxalate salt represented by the Formula LiPF(6-2q)(Ox)q, wherein Ox is an oxalate moiety and q is 1, 2 or 3; and c) optionally, at least one electrolyte salt. In some embodiments, the electrolyte composition comprises a mole ratio of Ox/P in the range of from 0.001 to 5. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.