Li-insertion into thin monolithic V₂O₅ films electrodes characterized by a variety of electroanalytical techniques

Slow-scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) have been simultaneously applied to study Li-ion intercalation into V₂O₅ films prepared by vacuum-deposition on Pt foils. The most prominent feature of their electrochemical behavior relates to sharp minima on D versus E plots, which are observed in the vicinity of very narrow cyclic voltammetric peaks. This was explained in the framework of a lattice-gas model with very high, attractive electron-ion interactions during Li-ion intercalation into the V₂O₅ electrode, as was already described for similar processes in graphite and some transition metal oxides: Li_xCoO₂, Li_xNiO₂, Li_xCo_yNi_1-yO₂ and Li_xMn₂O₄. Referring to the impedance spectra of the V₂O₅ electrodes, we show good agreement between the data obtained by the different techniques in the related time (or frequency) domains. This relates to both the differential intercalation capacity, C_int (low-frequency domain), and the chemical diffusion coefficient D (medium-frequency domain).