Electrochemical activation strategies of a novel high entropy amorphous V-based cathode material for high-performance aqueous zinc-ion batteries†

Abstract

V-based materials are widely applied as cathode materials for aqueous zinc-ion batteries because the high potential of V⁵⁺ provides a thermodynamic basis for the transition of Zn²⁺. The isotropy of high entropy amorphous vanadium oxide not only avoids the performance degradation caused by the broken crystal structure, but also offers more active sites and improves the solid-state solubility and transfer kinetics of Zn²⁺. Herein, a high entropy amorphous vanadium oxide@carbon matrix (V_xO_y@C) was obtained via a simple coprecipitation method. Two electrochemical activation strategies could induce the activation of amorphous V_xO_y@C as a high-performance cathode material for aqueous zinc-ion batteries (AZIBs). After electrochemical activation, the amorphous V_xO_y@C exhibited a high specific capacity of 399.1 mA h g^?1, high rate capability of 314.1 mA h g^?1 at 2.0 A g^?1 and excellent cycling stability for up to 300 cycles with a specific capacity retention of 91.8%. It was proven that the amorphous lump of V_xO_y@C transforms into an amorphous fibrous material accompanied by an increase in the valency of V. With the insertion of Zn²⁺, the fibrous materials would be reversibly converted into a lamellar structure.