General Oxygen Vacancy Engineering by Molten Zinc to Regulate Anode Redox for Durable Aqueous Zinc–Iodine Batteries

Oxygen vacancy engineering plays a crucial role in regulating surface chemistry for managing redox behaviors. However, controllable implantation of oxygen vacancy and safe and cost-effective production remain challenging. Herein, we report a general molten zinc reduction technology to prepare oxygen-deficient oxides with tunable vacancy content, synthetic universality, and industrial compatibility under mildly elevated temperature. Taking TiO2 as an example, theoretical study demonstrates thermodynamically favorable zinc affinity on TiO2 with increasing surface coverage supporting molten Zn supply. Featuring favorable electronic structures and inferior hydrogen evolution activity, TiO2-x nanoparticles were used to decorate aqueous Zn anodes, which demonstrate much improved cycling stability, verified by theoretical and in situ and ex situ investigations. Eventually, zinc-iodine batteries were assembled using modified Zn anodes, which achieved favorable cycling performance due to the regulated anode redox and alleviated self-discharge behaviors. This work provides a general oxygen vacancy engineering technology with an in-depth understanding for durable aqueous zinc batteries and related systems.