Oxygen vacancy-rich, binder-free copper pyrovanadate for zinc ion storage

[Display omitted] •A novel oxygen defect-rich binder-free highly crosslinked foam-like Cu3V2O7(OH)2⋅2H2O was prepared.•The Cu3V2O7(OH)2⋅2H2O cathode delivers high capacities and excellent long cycle stability.•Insight into the Zn-storage mechanism for the Cu3V2O7(OH)2⋅2H2O cathodes. The semiconductor nature of the vanadium oxide compound determines its low conductivity, which is not conducive to the transfer of electrons and affects the performance of an aqueous zinc ion battery (AZIB). Therefore, herein, an efficient strategy was proposed to improve the electrochemical performance of stainless steel (SS) supported highly crosslinked foam-like Cu3V2O7(OH)2⋅2H2O (CVO-SS-2) by creating oxygen vacancies. The effect of oxygen vacancy on the electrochemical behavior of Cu3V2O7(OH)2⋅2H2O grown on SS (Od-CVO-SS-2) was investigated. The experimental results show that the introduction of oxygen vacancies into the lattice significantly produces low oxidation state Cu and V species, thereby improving the conductivity and the interfacial activity of the Od-CVO-SS-2, promoting the reaction kinetics and enabling it to show more excellent electrochemical performance. Density functional theory (DFT) calculations confirmed that oxygen vacancy can effectively reduce the adsorption energy of Zn2+ ions. This means that the adsorption/desorption process of Zn2+ ions on Od-CVO-SS-2 is more reversible than that on pure CVO-SS-2. The Od-CVO-SS-2 electrode shows a high specific capacity of 269.2 mAh g−1 at a current density of 0.2 A g−1 after 100 cycles and excellent cyclic stability (88.2% retention after 3000 cycles 4 A g−1), higher than that of CVO-SS-2 (171.1 mAh g−1 at 0.2 A g−1). Besides, the energy storage mechanism of Zn2+ was studied by different ex-situ characterization methods. Vacancy design is an effective way to obtain electrode materials with excellent comprehensive properties.