Interface engineering of heterostructured vanadium oxides for enhanced energy storage in Zinc-Ion batteries

Rechargeable aqueous Zn-ion batteries (RAZIBs) with the merits of cost effectiveness and high safety have been rejuvenated as tantalizing energy storage systems to meet the demand for grid-scale applications. Currently, the energy storage capability of the positive electrode (cathode) holds the key for the overall performance of RAZIBs. In this work, we reveal VO2, V10O24.12H2O (HVO), and VO2/HVO can be prepared via hydrothermal reaction by using different reducing agents. VO2 exhibits high capacity of 237 mAh/g at 4 A/g, while it suffers from quick capacity decay with 48 % retention after 2000 charge/discharge cycles. On the contrary, HVO demonstrates moderate capacity but meritorious cycle stability (i.e., 173 mAh/g at 4 A/g and 82 % after 2000 cycles). By integrating the merits of high-capacity VO2 and high-stability HVO, the biphasic VO2/HVO sample exhibits promising electrochemical performance with high capacity (317 and 239 mAh/g at 1 and 4 A/g, respectively) and good cycle stability (80 % after 2000 cycles). As examined by band structure analysis, the superior electrochemical performance of VO2/HVO is attributed to the presence of a heterojunction between VO2 and HVO enabling a built-in electric field to boost electron transport kinetics, leading to high attainable capacity and reliable cycle performance in RAZIBs.