Zn V O ⋅1.8 H O Cathode Stabilized by In Situ Phase Transformation for Aqueous Zinc-Ion Batteries with Ultra-Long Cyclability.

Developing cathode materials integrating good rate performance and sufficient cycle life is the key to commercialization of aqueous zinc-ion batteries. The hyperstable Zn V O ⋅1.8 H O (ZVOH) cathode with excellent rate performance has been successfully developed via an in situ self-transformation from zinc-rich Zn V O (ZVO) in this study. Different from the common synthetic method of additional Zn pre-insertion, ZVOH is obtained from the insertion of structural H O and the removal of excess Zn in ZVO, ensuring the lattice structure of ZVOH remains relatively intact during the phase transition and rendering good structural stabilities. The ZVOH delivers a reversible capacity of 286.2 mAh g at 0.2 A g and of 161.5 mAh g at 20 A g over 18 000 cycles with a retention of 95.4 %, demonstrating excellent rate performance and cyclic stability. We also provide new insights on the structural self-optimization of Zn (CF SO ) (OH) ⋅n H O byproducts and the effect on the mobility of Zn by theoretical calculations and experimental evidence.