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

• The interlayer spacing of V 2 O 5 was adjusted through the intercalation of PEDOT. • V 2 O 5 interacts with PEDOT with the phase transition from Quinoid to Benzoid. • A reversible and fast Mg2+ ion storage of V 2 O 5 /PEDOT was achieved. • The enlarged interlayer and water activation improved the kinetic performances. • Bilayer structured V 2 O 5 /PEDOT achieved the high rate and cycling performances. 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 V 2 O 5 /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 19.02Å. Furthermore, the effect of water activation on the enhancement of the kinetics was confirmed by conducting electrochemical and in-situ/ex-situ characterizations. 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. [ABSTRACT FROM AUTHOR]