Water-steam activation toward oxygen-deficient vanadium oxides for enhancing zinc ions storage

A major limitation of vanadium oxides in aqueous Zn/V2O5 ion battery applications is that it suffers from strong Coulombic ion-lattice interactions with divalent Zn2+. Correspondingly, the vanadium oxides endow the poor utilization of its electrochemical active surface areas and unsatisfactory structure stability. Gibbs free energy of Zn2+ adsorption in the vicinity of oxygen vacancies can be reduced to thermoneutral value, which suggests the Zn2+ adsorption/desorption process on oxygen-deficient oxide lattice is more reversible as compared to a less defective vanadium oxide. In this work, it is demonstrated that these problems can be significantly ameliorated via creating oxygen vacancies in vanadium oxide host materials. Specifically, for the first time, vanadium oxides with abundant oxygen defects (labeled as Vo-V2O5) are fabricated via a new water-steam activation. Such water-steam activation constructs abundant oxygen defects, and the as-prepared materials shows a 3.5-fold increase in the carrier density, together with the larger electrochemical active surface areas compared to a less defective vanadium oxide. When used as cathode materials for aqueous zinc ion batteries, the Vo-V2O5 exhibit high specific capacity (335 mAh g-1 at 0.2 A g-1) and excellent cell stabilities (~87.2 % capacity retention after 3500 continuous charge/discharge cycles at 5.0 A g-1). Thus, this water-steam enhanced approach for disordered metal oxides, yields highly competitive cathode materials, which may also aid in the future development of advanced materials in related energy fields.