Sonochemical intercalation and polymerization of PEDOT:PSS into ammonium vanadate nanofibers for high-power zinc-ion batteries.

Zn-ion batteries(ZIBs) are promising candidates for next-generation energy storage systems due to their high stability, low cost and eco-friendliness. While vanadate is widely used as cathode materials in ZIBs, vanadate-based cathodes have been considered impractical for high-rate operation because of their low electrical conductivity, slow Zn ion diffusion kinetics, and the unsustainability of repetitive insertion and extraction at high current densities. In this study, PEDOT:PSS was successfully intercalated into the interlayers of ammonium vanadate nanofibers (EP-AVNF) using the sonochemical method, resulting in high performance for ZIBs with excellent rate capability and stability. Acoustic cavitation occurring under ultrasonic irradiation simultaneously induced oxolation and olation reactions leading to the growth of vanadate nanofibers, as well as in situ oxidative polymerization and interlayer intercalation of PEDOT:PSS, outcomes that were not obtained under silent (stirring-only) conditions. The presence of intercalated PEDOT:PSS not only efficiently expanded the structural interlayer of vanadate but also enhanced its electrical conductivity. Additionally, chemical bonding with vanadate accompanied the partial reduction of V5+ and the formation of vacancy-related defects. ZIBs utilizing the EP-AVNF cathode exhibited significantly improved electrochemical performance compared to those with pristine AVNF and PEDOT-intercalated AVNF. The EP-AVNF cathode demonstrated superior rate capability of 255mAh g-1 even at high current densities of 20 A g-1. Moreover, it achieved a capacity retention of 99.2 % after 1,000 cycles at 10 A g-1, along with high energy and power densities. This study indicates that the simultaneous intercalation and polymerization of PEDOT:PSS within the AVNF interlayer using the sonochemical method optimizes both structural and electrical characteristics with high efficiency, providing an efficient route for achieving high-rate and long-cycle ZIBs.