Mirrored Stability and Reversibility in the Local Structure of Hydrated Zn<i>x</i>V2O5 for Aqueous Zinc Ion Shuttling

Abstract The hydrated vanadium oxide intercalated with various ions continues to spark interest as a possible candidate for multivalent ion cathode hosts. The zinc vanadium bronze (ZnxV2O5-yH2Oy∼0.25) as a Zn-ion intercalation cathode shows excellent cycling and competitive energy density. This operando and ex situ study, using synchrotron-based X-ray absorption near-edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), and near-edge X-ray absorption fine structure (NEXAFS), investigates the local electronic and geometric structure of this candidate material during electrochemical cycling in an aqueous electrochemical in-situ cell. The study reveals a clear charge compensation process upon ion intercalation by tracking the V-K absorption edge. The cycling stability and high-rate recovery are also assessed by comparing early cycle X-ray absorption (XAS) data and post-rapid-cycling XAS data. These experiments evince significant, yet highly reversible, local chemical and structural changes in this hydrated zinc vanadium oxide for multivalent ion (de)intercalation.