Abstract
This article reports the evidence of surface film formation because of the breakdown of electrolyte upon high voltage cycling (4.9 V) of lithium rich cathode having a nominal composition of, Li1.2Mn0.525Ni0.175Co0.1O2. We studied the chemical composition of this passivation film using electrochemical impedance, X-ray Photoelectron and micro-Raman spectroscopy and the results were compared against the pristine electrode. In order to distinguish the changes in the surface films composition induced by prolonged electrochemical cycling versus chemical passivation effect, we also studied the surface composition of cathode powders aged with electrolytes at 60 oC. Our study shows that electrodes cycled beyond 150 cycles showed a rapid drop in capacity due to increase in the surface film resistance resulting in limited capacity utilization.
