Structural Oxygen Vacancies and Crystalline Defects in Iron Vanadate with Multiple Redox Centers Boosting Surface Migration for High‐Performance Zinc‐Ion Battery

Abstract

AbstractFe0.22V2O5(H2O)0.5 (FeVO) and Mn0.22V2O5(H2O)0.5 (MnVO) nanobelts with rich crystalline defects are synthesized by a facile one‐step hydrothermal approach. Their largest interlayer spacings are 10.6 Å and Rietveld refinement demonstrates the lamellar hydrated Fe3+ pillars in FeVO link different V–O–V layers via covalent bonds. Furthermore, all their V centers are five‐coordinated by O atoms, which is lower than the maximum coordination number of V (6), demonstrating that there are abundant oxygen vacancies (denoted as structural deficiency) in FeVO due to the lack of oxygen ligands, which can promote the migration of Zn2+ along the (001) surface of FeVO with a low energy barrier of 0.88 eV, as evidenced by density functional theory (DFT) simulations. FeVO exhibits an excellent capacity of 598 mAh g–1 at 0.1 A g–1 and long‐term cycling performance with a capacity retention of more than 80% over 1800 cycles at 5 A g–1, which is associated with the dual defects (structural oxygen vacancies and crystalline defects) and the extra capacity provided by the interconversion of Fe3+ ↔ Fe2+. Furthermore, a series of ex situ characterizations of the FeVO electrode reveal the co‐(de)intercalation of Zn2+/H+ and surface migration mechanism.