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

Abstract Fe_0.22V₂O₅(H₂O)_0.5 (FeVO) and Mn_0.22V₂O₅(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.