Simulations and Interpretation of Three-Electrode Cyclic Voltammograms of Pseudocapacitive Electrodes

Abstract

This study aims to provide physical interpretation of cyclic voltammograms obtained from pseudocapacitive electrodes using three-electrode systems. It presents numerical simulations based on a recent continuum model able to reproduce experimental CV curves obtained with different Nb2O5-based electrodes and LiClO4 in propylene carbonate as electrolyte. First, the respective contributions of faradaic and electric double layer charge storage mechanisms were clearly identified along with the associated faradaic and capacitive regimes. This was further illustrated by comparing CV curves for pseudocapacitive (Nb2O5) and EDLC (carbon) electrodes. Transition from the faradaic to the capacitive regime was caused by Li+ starvation at the electrode/electrolyte interface and the formation of ClO4− electric double layer. Moreover, the effects of electrode crystallinity on CV curves were reproduced and interpreted in terms of enhanced transport properties for lithium intercalation and electrode electrical conductivity. Finally, the electrode thickness featured an optimum corresponding to a compromise between accommodating large amounts of intercalated lithium and minimizing the potential drop across the electrode to drive faradaic reactions.