The study delivers detailed information about different lithium phases contributing to the complex surface chemistry of active electrodes in lithium ion batteries. Photoemission spectroscopy has been used to investigate the oxidation of metallic lithium as well as the reaction with air. From XP and UP valence band spectra characteristic emissions have been separated in order to help identifying lithium containing surface phases on intercalation electrodes. Characteristic spectral shapes of Li2CO3, Li2O2, Li2O and LiOH compounds are presented. The spectral features of a reacted lithium surface are compared to carbonate emissions on a LiCoO2 thin film cathode. (C) 2008 Elsevier B. V. All rights reserved.