Amorphization of Vanadium Oxides during the Reversible Insertion of Lithium.

The results of studying the structure and phase composition of thin-film positive electrodes of a lithium-ion battery based on vanadium oxides are presented. It is shown that initially polycrystalline films contain higher V2O5 and V3O7 oxides, the proportion of which increases with the time of oxygen annealing. As a result of charge–discharge cycling, the higher vanadium oxides are amorphized, while the content of the VO2 and V2O3 phases decreases slightly, and the proportion of VO oxide remains unchanged. These data are in good agreement with the change in the capacity of the films during their cycling, which suggests that the main reason for the decrease in the capacity of the films is the amorphization of the higher vanadium oxides with the highest specific capacity. [ABSTRACT FROM AUTHOR]