Defect-Rich Functional HfO 2-x for Highly Reversible Zn Metal Anode.

Interface engineering attracted tremendous attention owing to its remarkable ability to impede dendrite growth and side reactions in aqueous zinc-ion batteries. Artificial interface layers composed of crystalline materials have been extensively employed to stabilize the Zn anode. However, the diffusion kinetics of Zn 2+ in highly crystalline materials are hindered by steric effects from the lattice, thereby limiting the high-rate performance of the cell. Here, defect-rich HfO 2-x polycrystals derived from metal-organic frameworks (MOFs) (D-HfO 2-x ) are developed to enhance the Zn deposition behavior. The discrepancy of dielectric constants between metallic Zn and HfO 2 enables the building of an electrostatic shielding layer for uniform Zn deposition. More importantly, the oxygen vacancies in D-HfO 2-x provide abundant active sites for Zn 2+ adsorption, accelerating the kinetics of Zn 2+ migration, which contributes to the preferential exposure of the Zn (002) plane during plating. Consequently, the D-HfO 2-x -modified Zn anode delivers ultrastable durability of over 5000 h at 1 mA cm -2 and a low voltage hysteresis of 30 mV. The constructed defective coating provides a guarantee for the stable operation of Zn anodes, and the innovative approach of defective engineering also offers new ideas for the protection of other energy storage devices.