A room-temperature ionic liquid (RTIL) solvent, N-methyl, N-alkyl pyrrolidinium bis(trifluoromethanesulfonyl) amide (P-1X(Tf)(2)N), has been investigated for use in a lithium metal battery. An average cycling efficiency of >99% is achieved at 1.0 mA cm(-2) (I-dep=I-diss) on platinum. At deposition rates up to 1.75 mA cm(-2) optical micrographs indicate that the deposit is uniform and nondendritic. Above 1.75 mA cm(-2), the deposit becomes dendritic and efficiency decays. High cycling efficiency (>99%) can also be obtained on copper, but at relatively low current density (0.1 mA cm(-2)). The deposition/cycling history also influences the cycling behavior of the deposit. (C) 2004 The Electrochemical Society.