A surface layer formation on positive Li1+ x Mn2O4− δ thin film model electrodes as a result of electrochemical cycling procedures has been detected and characterized by scanning electron microscopy and X-ray photoemission spectroscopy. These thin film spinel electrodes, prepared by pulsed laser deposition, were cycled in 1M LiClO4 in propylene carbonate between 3.5 and 4.4V vs. Li/Li+ at 40°C and stopped at defined potentials and cycle numbers. The observed surface layers show, depending on the cycling conditions, a spotty and/or layered appearance and the fraction of this layer covering the cycled electrode depends on the charge potential and the number of electrochemical cycles.