The formation of a solid electrolyte interphase (SEI)-type layer on Li1.05Mn2O3.96 films prepared by pulsed laser deposition on Pt coated p-doped silicon and cycled in 1 M LiClO4 in propylene carbonate is reported. The formation of the SEI was studied as a function of the voltammetric charging/discharging sweep rate at 40 degrees C in the potential range of 3.5-4.4 V vs Li/Li+ using high resolution scanning electron microscopy and energy-dispersive X-ray spectroscopy. By applying an asymmetric charging/discharging cycle, it is possible to enhance the SEI layer formation. The observed cycling dependence of the SEI is indicative of a continuous formation and degradation process of the SEI depending on the cycling direction and the sweep rate. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3464798] All rights reserved.