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 Zn2+ ions and guest cations always results in finite insertion ability of Zn2+ ions and low specific capacity. Herein, Zn3(VO4)2 with Zn─V─O vacancy clusters (Zn3(VO4)2-VZVO) 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 Zn2+ and H+ ions, reduce the inherent electrostatic interaction, and contribute the dominative capacity through abundant unsaturated coordination oxygen atoms. Additionally, part of adsorbed Zn2+ ions can reversibly intercalate Zn3(VO4)2-VZVO and transform into Zn3V2O7(OH)2·2H2O to contribute the remaining capacity. Consequently, the optimized Zn3(VO4)2-VZVO 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 Zn3(VO4)2-VZVO cathode, but also offers new insight to design high-performance cathode materials for AZIBs.
Chi et al. (Thu,) studied this question.