Hydration‐Driven Structural Heterogeneity for Robust Zn 2+ Storage in Vanadium Oxide Cathodes

Abstract Interlayer modification can effectively tailor the local environment of vanadates and enhance ion migration kinetics in aqueous zinc‐ion batteries (ZIBs). However, the regulation of various intercalants on the Zn 2+ insertion mechanism and the resulting precise phase evolution are still unknown. Based on the findings, pre‐intercalated Y 3+ ion generates the transition from stable [V 5+ O 5 ] to the metastable [V 4+ O 5 ] due to the charge balance. Interlayer water induces local structure change from [V 4+ O 5 ] to [V 4+ O 6 ], resulting in the reconfiguration from monolayer α‐V 2 O 5 to heterogeneous bilayer δ‐V 2 O 5 ·nH 2 O structure. Notably, the Zn 2+ storage behavior of vanadium is governed by the local structural transformation from [VO 5 ] pyramids to [VO 6 ] octahedra. Correspondingly, the Y‐doped monolayer α‐V 2 O 5 transforms into a wavy‐like γ‐V 2 O 5 , whereas water‐doped bilayer δ‐V 2 O 5 ·nH 2 O maintains its original crystal structure with only interlayer spacing variation. In other words, interlayer water promotes the formation of a stable bilayer structure, preventing lattice distortion and phase transitions during Zn 2 ⁺ insertion/extraction, thereby effectively enhancing cycling stability. The co‐doped V 2 O 5 exhibits a capacity of ≈400 mAh g −1 at 0.1 A g −1 , and an outstanding capacity retention of ≈90% over 3000 cycles. This work offers valuable insights into the local environment modification of advanced cathode materials.