Boosting zinc-ion storage in vanadium oxide via“dual-engineering” strategy

Vanadium oxide, with large interlayer spacing and variable oxidation state, has been widely favored by researchers as a promising cathode material for aqueous zinc ion batteries (ZIBs), but its non-ignorable disadvantages such as slow zinc ion diffusion kinetics, fragile structure, and poor electrical conductivity limit the practical application. Herein, it is found via density functional theory (DFT) calculation that the simultaneous introduction of oxygen vacancies and crystalline water can not only improve the conductivity of the vanadium oxide but also significantly reduce the diffusion energy barrier in the process of Zn2+ (de)intercalation. Hence, we employed a feasible over-reduction solvothermal method to introduce more oxygen vacancies and crystalline water into Od-V2O5·4VO2·0.82 H2O (denoted as VHO). Based on the synergistic benefits of this dual engineering strategy, the VHO cathode exhibits impressive performance metrics (194.5 mAh g−1 at 20.0 A g−1). Further, systematic ex-situ characterizations reveal a mechanism for the sequential dominance of Zn2+/H+ (de)intercalation in the VHO cathode, i.e., insertion of Zn2+ dominates high voltages (1.40 −0.70 V) and H+ dominates low voltages (0.70 −0.20 V). The convenient dual-modification strategy is a hopeful one to put forward the application of ZIBs.