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.