Described are electrolyte compositions containing a non-fluorinated carbonate, a fluorinated solvent, a cyclic sulfate, at least one lithium borate salt selected from lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, or mixtures thereof, 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 composition may further comprise a fluorinated cyclic carbonate. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.