Ethyl 3,3,3-trifluoropropanoate (TFPE) is an additive that extends the life of the LiMn2O4/Li cell. After 200 charge and discharge cycles at 55 °C, a LiMn2O4/Li cell increases the capacity retention by 13.2% (48.2% without additive versus 61.4% with additive) when 0.5 vol% TFPE is added to the electrolyte. Versus TFPE-free cells, the additive inhibits the formation of HF induced erosion of the LiMn2O4 electrode and reduces the interfacial impedance by 61.2% (drops to 139 from 227 Ohm).