Jump diffusion coefficient of different cations intercalated into amorphous WO3

This work shows how the combination of quasi-equilibrium (chronopotentiometry) and kinetical measurements (electrochemical impedance) is able to extract ionic mobility values like the jump diffusion coefficient DJ. Results are presented on the jump diffusion coefficient variation with composition of several cations (Li+, Na+, and K+) intercalated into electron beam evaporation-prepared a-WO3 thin films. DJ exhibits higher values for the smallest ion (Li+), and decreases as the ion size enlarges. In all cases DJ shows lower values for high intercalation levels. It is noted that the type of cation rather influences transport mechanisms than equilibrium properties (insertion thermodynamics). The energy barrier of ion hopping is analyzed in light of available microscopic diffusion models and theoretical simulations.