An EIS study, on LixNi0.75Co0.25O2 interaction cathode has been performed. The spectra have been interpreted on the basis of an equivalent circuit based on a combination of a Voigt-type analog (Li ion migration through surface film and charge transfer) in series with a Warburg type element, an element that takes into account the electronic resistance of the material and a capacitor (Li accumulation). (C) 2001 Elsevier Science B.V. All rights reserved.