Li+ insertion into pure and doped amorphous WO3 films. Correlations between coloration kinetics, charge and mass accumulation

Transient time and frequency techniques were used in this study to evaluate the improvements in Li+ charge and mass intercalation kinetics resulting from the chemical modification of amorphous WO3 host materials by the addition of LiCF3SO3 during film synthesis. The improved performance of charge transfer and mass kinetics of doped films was coupled with an improvement in their optical absorption kinetics. The chemically modified amorphous WO3 films also showed a high charge, mass and optical absorption capacity, a behavior that is better understood in light of a recent interpretation based on an approach consisting of an ion-trapping charge mode that exists in addition to the other charge modes, such as ion diffusion through the host lattice. The ion-trapping charge is a slow charge mode relating to the coloration sites, while the diffusion is fast and is not related to coloration. These are the two main charge modes contributing to the filmsʹ kinetics.