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.

Recently, vanadium dioxide (VO) has been recognized as one of the most prospective cathodes for aqueous zinc ion batteries (AZIBs) for its high reversible specific capacity; nevertheless, its Zn diffusion kinetics and cycling stability have not yet met expectations. Herein, Mo ions are introduced into VO to optimize the intrinsic electronic structure and micromorphology of VO, achieving significantly enhanced zinc-ion storage. It is found that the substitution of Mo for V narrows the band gap of VO and thus enhances the conductivity of the material, while VO nanorods are transformed into VO 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 Zn. Consequently, the Mo-substituted VO (0.5-Mo-VO) 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 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.