Described are electrolyte compositions comprising a fluorinated solvent, an organic carbonate, a sultone, and optionally a borate. The fluorinated solvent may be a fluorinated acyclic carboxylic acid ester, a fluorinated acyclic carbonate, a fluorinated acyclic ether, or mixtures thereof. The organic carbonate may be fluorinated or non-fluorinated. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.