Described herein are electrolyte compositions containing an organic carbonate, a fluorinated solvent, a cyclic sulfate, and at least one electrolyte salt. The cyclic sulfate can be represented by the formula: wherein each A is independently a hydrogen or an optionally fluorinated vinyl, allyl, acetylenic, propargyl, or C1-C3 alkyl group. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.