Conductive polymer-modified sodium ion intercalation in vanadium pentoxide for high performance zinc-based batteries

Vanadium pentoxide (V2O5) garners attention as cathode in zinc ion batteries (ZIBs) for its multi-electron redox reactions and high reversible capacity (>300 mAh/g), cost-effectiveness, and diverse crystal structures. However, inferior cycling stability stemming from limited electron conductivity and sluggish divalent Zn2+ diffusion in crystal structure largely hinders its practical application. In this study, a sodium-ion-embedded vanadium pentoxide (Na2V6O16) cathode material (NVO) was synthesized via a simple hydrothermal method to expand the interlayer spacing, which allows facile diffusion of Zn2+. Furthermore, surface coating with poly(3,4-ethylenedioxythiophene) (PEDOT) was conducted to improve conductivity and protect active material from dissolving into electrolyte during charge-discharge. As a result, the assembled Zn||NVO@PEDOT exhibited a reversible discharge capacity of 301.0 mAh/g at 1 A/g, maintaining 137.2 mAh/g over 600 cycles, outperforming the Zn batteries with commercial V2O5. Even under a high current density of 10 A/g, NVO@PEDOT still delivered a high capacity of 147.4 mAh/g after 150 cycles. This study provides innovative insights aimed at improving the electrochemical capacity and stability of cathode materials for aqueous zinc batteries.