Fast and reversible zinc ion intercalation in Al-ion modified hydrated vanadate

Aqueous Zn-ion batteries (ZIBs) are emerging candidates for safe and eco-friendly large-scale energy storage, but the critical challenge is to develop stable and robust cathode materials for reversible and fast Zn2+ intercalation. In the present work, the drawbacks of pure hydrated vanadium oxides (VOH), including low ion mobility and cycling instability, are mitigated by modifying the local atomic environment and increasing the amount of tetravalent vanadium cations. These effects are achieved by introducing trivalent Al-ions during a one-step hydrothermal synthesis. The expanded lattice spacing and improved conductivity of the synthesized Al-VOH enable rapid Zn2+ diffusion and electron transfer, leading to a high capacity of 380 mAh.g(-1) at 50 mA g(-1), as well as the excellent long-term cycling stability (capacity maintained over 3000 cycles). Further investigations of the reaction kinetics and mechanism reveal the effects of introducing Al-ions, and the role of Zn2+ trapped upon initial charging plays in promoting the subsequent electrochemical process and preventing the structural degradation.