Disclosed herein are electrolyte compositions comprising a fluorinated solvent, at least one silyl oxalate represented by the formulas RR′Si(C2O4), wherein R and R′ are each the same or different from each other and independently selected from C1-C8 alkyl, C2-C8 alkenyl, C2-C8 alkynyl, or C6-C10 aryl radical, optionally comprising at least one substituent selected from halogen, hydroxyl, alkoxy, carbonyl, and carboxyl groups; and LiPF6. Also disclosed herein are electrolyte compositions comprising a fluorinated solvent and a lithium oxalato phosphate salt represented by the formula LiPF(6-2q)(C2O4)q, wherein q is 1, 2 or 3; wherein the oxalato phosphate salt comprises at least a portion that is derived from at least one silyl oxalate as defined herein. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.