Zn0.52 V2 O5-a ⋅1.8 H2 O Cathode Stabilized by In Situ Phase Transformation for Aqueous Zinc-Ion Batteries with Ultra-Long Cyclability.

Abstract

Developing cathode materials integrating good rate performance and sufficient cycle life is the key to commercialization of aqueous zinc-ion batteries. The hyperstable Zn0.52 V2 O5-a ⋅1.8 H2 O (ZVOH) cathode with excellent rate performance has been successfully developed via an in situ self-transformation from zinc-rich Zn3 V3 O8 (ZVO) in this study. Different from the common synthetic method of additional Zn2+ pre-insertion, ZVOH is obtained from the insertion of structural H2 O and the removal of excess Zn2+ 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-1 at 0.2 A g-1 and of 161.5 mAh g-1 at 20 A g-1 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 Znx (CF3 SO3 )y (OH)2x-y ⋅n H2 O byproducts and the effect on the mobility of Zn2+ by theoretical calculations and experimental evidence.