LITHIUM-ION ELECTROCHEMICAL CELLS INCLUDING FLUOROCARBON ELECTROLYTE ADDITIVES

Lithium-ion electrochemical cells are provided that include a positive electrode that includes a lithium metal oxide or a lithium metal phosphate, a negative electrode capable of intercalating or alloying with lithium, and an electrolyte that includes an additive. The additive includes a multifunctional anion that has the formula, X-SO2-Rf′-SO2-Y, wherein X and Y are, independently, either O- or RfSO2N-, Rf is a straight or branched fluoroalkyl moiety having from 1 to 6 carbon atoms, and can, optionally, contain one or more in-chain heteroatoms, wherein Rf′ is a straight or branched chain or cyclic fluoroalkylene having from 1 to 10 carbon atoms and can, optionally, contain one or more in-chain heteroatoms, and wherein both Rf and Rf′ have a maximum of 20% non-fluorine substituents. The provided additives can improve the performance, hydrolytic stability, and thermal stability of the provided electrochemical cells.