Simultaneous in-situ conductivity and cyclic voltammetry characterization of Li-ion intercalation into thin V₂O₅ films

Cyclic voltammetry (CV) and in-situ electronic conductivity curves have been simultaneously measured during Li-ion insertion/de-insertion into/from thin, partially crystallized, Li_xV₂O₅ film in 1 M LiBF₄ + propylene carbonate solution. A similarity has been observed between the CV curves and the plots of the derivative of conductivity, dσ/dE, versus potential. A semi-metal-to-insulator transition, and vice versa, has been observed (in intercalation and de-intercalation, respectively), ascribed to the ε- to δ-phase transition of Li_xV₂O₅. This transition is accompanied by an increase in the V-V distance between adjacent VO₅ layers, and is probably responsible for the decrease in the film conductivity, realized via electron hopping between the high-and low-valence vanadium sites.