In order to assess the effect of the scanning rate upon the Li+ ion diffusion coefficient, as found using cyclic voltammetry, a series of experiments was carried out at various rates (2, 5, 10, 20 or 50mV/s) for the same WO3 film prepared by electron gun deposition at room temperature. The diffusion coefficient for Li-ion intercalation into the WO3 film, calculated using the Randles–Sevcik equation, was compared with that calculated by using the galvanostatic intermittent titration technique; carried out on the same WO3 film. It was found that, at high scanning rates (above 2mV/s), the Randles–Sevcik method tended grossly to over-estimate the diffusion coefficient; due possibly to the occurrence of large potential gradients within the WO3 film. When compared to the results deduced from galvanostatic intermittent titration, the voltammetric diffusion coefficient was found to be up to 67% higher. It was therefore concluded that diffusion coefficient values deduced from cyclic voltammetry peaks, using the Randles–Sevcik method, had to be treated with caution and that scanning rates below 2mV/s were required in order to obtain reliable results.

Dependence of the Estimated Diffusion Coefficient of LixWO3 Films on the Scan Rate of Cyclic Voltammetry Experiments. G.Leftheriotis, S.Papaefthimiou, P.Yianoulis: Solid State Ionics, 2007, 178[3-4], 259-63