Accelerating the kinetics of zinc-ion diffusion via redox-active polyaniline intercalated vanadium oxide for green durable zinc-ion batteries

Layered vanadium pentoxide (V₂O₅) has caused considerable attention owing to rich redox chemistry of vanadium that enables high specific capacities in aqueous zinc batteries. However, it is still confronted with inherent narrow interlayer spacing, poor conductivity and sluggish diffusion kinetics of Zn²⁺ due to the strong electrostatic interactions in layered V₂O₅. Herein, we propose a high-capacity nanosheet cathode by preparing an in-situ intercalation polymerization of Fe(CN)₆⁴⁻-doped polyaniline within the interlayers of V₂O₅ to expand the interlayer spacing and provide abundant active site, which enables highly reversible and ultrafast zinc ions (de)intercalation processes. Especially, the spontaneous formation of zinc ferricyanide Zn_x+1[Fe^III/II(CN)₆] within the polyaniline framework acting as a redox mediator exhibited faster Zn²⁺ (de)intercalation kinetics by catalyzing the reduction of V₂O₅ during discharging process, thereby shortening the Zn²⁺ diffusion path and accelerating its diffusion kinetics. Moreover, this nanosheet cathode can deliver a high specific capacity of 503 mAh g⁻¹ at 0.5 A g⁻¹ and exhibit a capacity retention of 92 % over 3000 cycles at 1.5 A g⁻¹. The remarkable electrochemical performance is attributed to the layered structure of Fe(CN)₆⁴⁻-PANI-V₂O₅ constructed with large interlayer spacing and active filler, which enables the rapid (de)intercalation of zinc ions with a negligible structure change.