Interfacial Fluorinated Ion Crowding Enables Reversible Zinc Metal Batteries

Aqueous zinc metal batteries (AZMBs) are promising candidates for large-scale energy storage owing to their intrinsic safety. However, their lifespan is severely limited by side reactions such as dendrite growth and hydrogen evolution at the Zn-electrolyte interface. Conventional single-electrolyte-additive approaches are thermodynamically constrained, yielding only insufficient coverage of the inner-Helmholtz plane (IHP) and poor control of interfacial reactions. Here, we report an interfacial fluorinated-ion crowding strategy by simultaneously introducing multiple low-concentration fluorinated additives. Computational and spectroscopic analyses reveal that various-sized F-groups densely occupy the IHP, displacing water molecules and homogenizing Zn²⁺ flux. This emergent crowding effect, inaccessible to single-additive strategies, enables unprecedented interfacial regulation. Electrochemical tests demonstrate ultrastable Zn plating/stripping over 1200 h at 5 mA cm^-2 and 1800 h at 10 mA cm^-2, more than tenfold longer than the baseline electrolyte. This work establishes interfacial ion crowding as a powerful design principle, rooted in fundamental electrochemistry, offering a pathway toward high-performance and durable AZMBs.