Lithium-metal batteries with LiFePO4 cathodes and a polymer electrolyte consisting of poly(ethylene oxide), LiTFSI, and a room temperature ionic liquid are demonstrated to have exceptional performance at 40degreesC. This low operating temperature is made possible by the dramatically improved Li+ cation transport in the polymer electrolytes. These electrolytes are flexible, slightly tacky membranes with high ionic conductivities, excellent mechanical properties and exceptional electrochemical stability. No solvent was used to prepare the materials and the electrolytes have no volatile components. (C) 2005 The Electrochemical Society.