Degradation mechanisms in low-voltage Wadsley–Roth TiNb2O7 electrodes upon cycling with Li

Abstract

Drawing more and more interest, Wadsley–Roth phases, and more specifically titanium-niobium oxide (TNO), are considered serious competitors of Li₄Ti₅O₁₂ exhibiting a higher capacity and thus a larger specific energy. Many groups reported advanced synthesis routes for this material but only a little consideration was given to the study of the lithiation and degradation mechanisms. In this work, we report a singular evolution in the cycling performance of TiNb₂O₇, synthesized with a normal solid-state route. Indeed, performances at high rates are strongly varying depending on its cycling history. To understand the underlying phenomena, we carried out many investigations, in particular by coupling in situ and post mortem structural characterization studies.