This article reports the evidence of surface film formation due to the oxidation of electrolyte upon high voltage cycling (4.9 V) of the lithium rich cathode, Li1.2Mn0.525Ni0.175Co0.1O2. We have studied the chemical composition of this surface film using electrochemical impedance, X-ray Photoelectron and micro-Raman spectroscopies and the results are compared against the pristine electrode. In order to distinguish the changes in the surface film composition induced by prolonged electrochemical cycling versus chemical passivation effect, we studied the surface composition of cathode powders aged with electrolytes at 60 degrees C. Our results show that after 150 cycles, the electrodes showed a rapid drop in capacity due to increase in the surface film resistance resulting in limited capacity utilization. (C) 2012 Elsevier B.V. All rights reserved.