An XAS Study for Understanding Charge Storage Mechanism of Hybrid AC-Decavanadate Electrode Material

Polyoxovanadates can be utilised for both high power and energy applications thanks to their multi-electron transfer during charge-discharge but suffer from extremely poor cyclability. A novel approach involving the in-situ synthesis of decavanadate within activated carbon pores has successfully improved both long-term cyclability and ultra-fast charge transfer kinetics. Electrochemical tests show that these hybrid materials can performed better as anodes in asymmetric supercapacitors. However, the total number of electrons when they act either as positive or negative electrodes is not clear; therefore, the utilization rate is unknown. Besides, vanadium has several oxidation states which could coexist within the POM structure. This study aims to investigate the number of electrons and oxidation states involved in charge and discharge processes in these materials through operando XAS measurements to understand their higher stability and rate capability.