A newly developed imide electrolyte salt, LiN(C2F5SO2)(2) (LiBETI) was found to give very uniform. thin. and stable surface films on a lithium metal electrode in the propylene carbonate (PC) solution. LiBETI/PC was studied and compared to determine its ability to form such a stable surface film, with conventional electrolyte systems such as LiCF3SO3/PC, LiPF6/PC, and LiN(CF3SO2)(2)/PC (LiTFSI/PC). The surface film formed in LiBETI/PC system was a hemispherical, and the composition of the film consisted mainly of LiF, which is similar to that in a LiPF6/PC system. Quartz crystal microbalance (QCM)and cyclic voltammetry (after the: tenth cycle) indicated that the surface film formed in LiBETI/PC (ca. 50 nm) was thinner than those in LiPF6/PC (ca. 90 nm), LiTFSI/PC (ca. 140 nm), or LiCF3SO3/PC (ca 255 nm). The variation of the resonance resistance (Delta R) obtained from in situ CV/QCM measurement, which has been demonstrated to be a good measure of the surface roughness, also suggested that LIBETI/PC system gave a compact and smooth surface topology during lithium deposition-dissolution cycles. impedance spectroscopy together with preliminary cycling tests showed that the LiBETI/PC system provides the highest cycling efficiency and improved cycleability among existing electrolyte salt systems in rechargeable battery systems employing lithium metal anodes.