Abstract: The effect of solvents and cations of H⁺ and Li⁺ on the- electrochromic stability and process at the WO₃ anodic, oxide film were investigated by using cyclic chronocoulometry, cyclic voltamme-try, in situ UV/Vis reflectance spectroscopy and photocurrent spectroscopy.The parameters of hydrogen or lithium accumulation amount in the film and the number of the transient perods which can be determined from the Q_t transient can be characteristic of the stability of the film, It can be found that the electrochromic system of W/WO₃/LiClO₄ solution in acetonilrile has a high stability.The in-terfacial electrochemical mechanism of the injection-extraction of Li ions in the electrochromic process is quite different from H⁺ ions.The color center for the anodic oxide film WO₃ is considered to be the free electrons whose density is over 10²¹/cm³ and the optical transition, i.e, coloring process, arises from the plasma oscillation.

Key words: Electrochromism, Tungsten trioxide film, Electrochromic lifetime, Cyclic chronocoulome-try, Electroreflectance spectrum