Aiming at improving the electrochromic properties of NiO thin films, well-known as anodic counter electrodes, the effect of tungsten addition was investigated. Ni-W-O thin films were deposited by pulsed laser deposition in optimized conditions, namely a 10(-1) mbar oxygen pressure and a room temperature substrate. The presence of W led to a progressive film amorphization. An increase in cyclability for Ni-W-O (5%(t) WO3) electrode, cycled in KOH I M electrolyte, was associated with a limited dissolution of the oxidized phases with tungsten addition. HRTEM investigations of cycled films revealed that the stabilization is correlated to the existence of an alpha(II) hydroxide phase. (c) 2005 Elsevier B.V. All rights reserved.