Unsaturated Coordination Oxygen in Zn─V─O Vacancy Clusters Enables Superb Zinc Storage Capability

ABSTRACT Vanadates have been extensively applied in aqueous zinc‐ion batteries (AZIBs) for the enlarged interlayer spacing and rich active sites induced by the pre‐intercalation of metal or ammonium ions. However, the strong electrostatic interaction between Zn ²⁺ ions and guest cations always results in finite insertion ability of Zn ²⁺ ions and low specific capacity. Herein, Zn ₃ (VO ₄ ) ₂ with Zn─V─O vacancy clusters (Zn ₃ (VO ₄ ) ₂ ‐V _ZVO ) is innovatively prepared as cathode material for AZIBs. Based on the ab initio molecular dynamics (AIMD) simulations and comprehensive characterizations, the Zn─V─O vacancy clusters are demonstrated to effectively capture most of free Zn ²⁺ and H ⁺ ions, reduce the inherent electrostatic interaction, and contribute the dominative capacity through abundant unsaturated coordination oxygen atoms. Additionally, part of adsorbed Zn ²⁺ ions can reversibly intercalate Zn ₃ (VO ₄ ) ₂ ‐V _ZVO and transform into Zn ₃ V ₂ O ₇ (OH) ₂ ·2H ₂ O to contribute the remaining capacity. Consequently, the optimized Zn ₃ (VO ₄ ) ₂ ‐V _ZVO cathode delivers high reversible capacity of 410 mAh g ⁻¹ at 1.0 A g ⁻¹ and satisfying capacity retention of 94.1% after 800 cycles at 0.1 A g ⁻¹ . This study not only reveals the formation and action mechanism of unsaturated coordination oxygen sites in Zn ₃ (VO ₄ ) ₂ ‐V _ZVO cathode, but also offers new insight to design high‐performance cathode materials for AZIBs.