Synergistic Oxygen Defect Engineering and Neodymium-Ion Intercalation Endows MIL-88B(V)-Derived V2O5 with Fast Diffusion Kinetics and Enhanced Cycling Stability for Aqueous Zinc-Ion Batteries

Vanadium-based oxides with unique layered structures and multiple oxidation states have attracted considerable attention for aqueous zinc-ion batteries (AZIBs). However, the inferior conductivity and nearly nonporous structural characteristics of commercial V2O5 inevitably hinder the transport of electrons/ions, and the inherently narrow interlayer spacing and strong electrostatic interactions severely restrict the further development of V2O5 cathodes. In this work, neodymium (Nd) ions were employed as guests to intercalate into MIL-88B(V)-derived V2O5 (denoted as OV-NVO) by a one-step hydrothermal process and as stable cathode materials for AZIBs. Benefiting from its well-designed honeycomb-like porous structure, large surface area, expanded interlayer spacing, abundant oxygen vacancies, and feeble electrostatic interactions, the OV-NVO cathode delivered a prominent discharge capacity of 455.2 mAh g-1 at 0.1 A g-1 and exhibited satisfactory rate capability (341.5 mAh g-1 at 5.0 A g-1) and cycling stability (90.8% capacity retention after 2000 cycles at 5.0 A g-1). Impressively, the assembled Zn//OV-NVO flexible battery can operate stably under extreme bending conditions and exhibits superior electrochemical behavior. Furthermore, the reversible Zn2+ storage mechanism and structural evolution of the OV-NVO cathode were further analyzed by kinetic analysis, ex situ characterizations, and density functional theory calculations. This synergistic strategy by combining Nd-ion intercalation and oxygen defect engineering provides an effective approach to the design of high-performance vanadium-based cathode materials, offering more possibilities for the practical applications of AZIBs.