X-ray photoelectron spectroscopy with synchrotron radiation has been used to investigate the reactivity of adsorbed diethyl carbonate (DEC) with the cathode material LiCoO2 (LCO). Adsorption experiments and preparation of thin film electrodes have been carried out in ultra high vacuum conditions. The thin film cathodes have been prepared on titanium substrates by radio frequency sputtering. The initial interaction, adsorption and reaction of DEC with LCO were observed at 133 K. Chemical and physical adsorptions and also chemical reaction of DEC in the adsorption layer are detected. (c) 2012 Elsevier B.V. All rights reserved.