Molybdenum-optimized electronic structure and micromorphology to boost zinc ions storage properties of vanadium dioxide nanoflowers as an advanced cathode for aqueous zinc-ion batteries

Abstract

Recently, vanadium dioxide (VO2) has been recognized as one of the most prospective cathodes for aqueous zinc ion batteries (AZIBs) for its high reversible specific capacity; nevertheless, its Zn2+ diffusion kinetics and cycling stability have not yet met expectations. Herein, Mo ions are introduced into VO2 to optimize the intrinsic electronic structure and micromorphology of VO2, achieving significantly enhanced zinc-ion storage. It is found that the substitution of Mo for V narrows the band gap of VO2 and thus enhances the conductivity of the material, while VO2 nanorods are transformed into VO2 nanoflowers which are self-assembled from ultra-thin nanosheets after the introduction of Mo, exposing much more active sites to enhance the migration kinetics of Zn2+. Consequently, the Mo-substituted VO2 (0.5-Mo-VO2) exhibits excellent electrochemical properties, presenting a high initial capacity of 494.5 mAh/g at 0.5 A/g, excellent rate capability of 336 mA h g−1 at 10 A/g and brilliant cycling stability with the capacity retention of 82% over 2000 cycles at 10 A/g. This work provides significant guidance for the design of advanced cathodes for AZIBs by optimizing the electronic structure and tailoring morphology of V-based materials.