Intercalation of bilayered V2O5 by electronically coupled PEDOT for greatly improved kinetic performance of magnesium ion battery cathodes

Magnesium ion batteries (MIBs) are attracting attention as promising alternatives to next-generation energy storage systems owing to their high safety, high volumetric capacity, low reduction potential, abundant raw materials, and economic efficiency. However, developing highly reversible and kinetically fast MIB cathode materials is very challenging owing to the sluggish Mg2+ ion diffusion and low reversible capacity typical of bivalent magnesium ions, as well as the strong electrostatic interactions with the host cathode material. Herein, we designed a charge transfer interaction of a bilayered V2O5/PEDOT (VOP) complex with involving the phase transition of PEDOT from a quinoid to a benzoid structure which could be realized because of reversible and fast Mg2+ ion storage through an enlarged interlayer spacing of 19.02A. Furthermore, the effect of water activation on the enhancement of the kinetics was confirmed by conducting electrochemical and in-situ/ex-situ charac-terizations. Consequently, the as-designed VOP electrodes delivered a high specific capacity of 339.7 mAh/g at 100 mA g-1, high-rate capacity of 256.3 mAh/g at 500 mA g-1, and long-term cyclic stability with a 0.065 % decay rate and high capacity of 172.5 mAh/g after 500 cycles.

Automated summary

Magnesium ion batteries (MIBs) are attractive as next-generation energy storage systems due to their high safety, capacity, low reduction potential, material abundance, and economic efficiency. However, developing reversible and fast MIB cathode materials is challenging due to slow ion diffusion and weak interactions. In this study, a V2O5/PEDOT (VOP) complex with charge transfer interaction and an expanded interlayer spacing of 19.02A was designed to enable reversible and fast Mg2+ ion storage. Water activation was found to enhance the kinetics. The VOP electrodes exhibited high specific and high-rate capacity, as well as long-term cyclic stability.