A study is conducted of the performance of lithium iron(II) phosphate, LiFePO4, as a cathode material in a lithium secondary battery that features an ionic liquid electrolyte solution and a metallic lithium anode. The electrolyte solution comprises an ionic liquid of a N-methyl-N-alkyl-pyrrolidinium (alkyl=n-propyl or n-butyl) cation and either the bis(fluorosulfonyl)imide [(FSO2)(2)N-] or bis(trifluoromethanesulfonyl)imide [(F3CSO2)(2)N-] anion. together with 0.5 mol kg(-1) of lithium bis(trifluoromethanesulfonyl)imide salt. For N-metliyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide, coin cells discharging at rates of C/10 and 4C yield specific capacities of 153 and 110mAhg(-1), respectively, at an average coulombic efficiency of 99.8%. This performance is maintained for over 400 cycles at 50 degrees C and therefore indicates that these electrolyte solutions support long-term cycling of both LiFePO4 and metallic lithium while, due to the negligible volatility of ionic liquids, surrounding the lithium in an inherently safe. non-flammable medium. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.