Transparent CeO2 thin solid films, used as ion storage layer in electrochromic devices were prepared by the sol-gel method using a alkoxide route combined with the dip-coating technique. The precursor sol was prepared from a mixture of cerium (IV) methoxyethoxide in anhydrous 2-butanol. Electrochemical Li+ intercalation/deintercalation was performed by cyclic voltammetry and the results indicate that the CeO2/LiClO4 system is electrochemically reversible. The total inserted/extracted charge of the CeO2 film was determined by chronoamperometric measurements, which showed an ion storage capacity of similar to 14 mC/cm(2). The solid-state diffusion of lithium ion into the CeO2 thin films was investigated by electrochemical impedance spectroscopy. (c) 2007 Elsevier B.V. All rights reserved.