Anodic Oxidation Strategy toward Structure-Optimized V₂O₃ Cathode <i>via</i> Electrolyte Regulation for Zn-Ion Storage.

Abstract

The lack of suitable cathodes is one of the key reasons that impede the development of aqueous zinc-ion batteries. Because of the inherently unsuitable structure and inferior physicochemical properties, the low-valent V₂O₃ as Zn²⁺ host could not be effectively discharged. Herein, we demonstrate that V₂O₃ (theoretical capacity up to 715 mAh g^-1) can be utilized as a high-performance cathode material by an <i>in situ</i> anodic oxidation strategy. Through simultaneously regulating the concentration of the electrolyte and the morphology of the V₂O₃ sample, the ultraefficient anodic oxidation process of the V₂O₃ cathode was achieved within the first charging, and the mechanism was also schematically investigated. As expected, the V₂O₃ cathode with a hierarchical microcuboid structure achieved a nearly two-electron transfer process, enabling a high discharging capacity of 625 mAh g^-1 at 0.1 A g^-1 (corresponding to a high energy density of 406 Wh kg^-1) and cycling stability (100% capacity retention after 10 000 cycles). This work not only sheds light on the phase transition process of low-valent V₂O₃ but also exploits a method toward design of advanced cathode materials.