Ultrathin Yet Effective: 90-nm ZnF2 Layer for Stabilizing Zinc-Metal Batteries

The practical use of aqueous zinc-ion batteries is limited by dendrite formation and interfacial degradation at the Zn-metal anode. Here, we demonstrate that an ultrathin ZnF ₂ interfacial coating —merely 90 nm thick—significantly enhances anode stability by suppressing side reactions, promoting uniform Zn deposition, and providing moderate mechanical adhesion. Symmetric cells with ZnF ₂ -coated Zn achieved lifespans of 1500 hours at 0.5 mA cm ⁻² and 500 hours at 3.0 mA cm ⁻² . Full cells with Mn _x V ₂ O ₅ cathodes retained 82% capacity after 2000 cycles. Crucially, nanoscratch tests revealed that the optimum thickness of ZnF ₂ films provided reasonable interfacial toughness, offering new insights into the mechanical–electrochemical co-design of artificial protective layers – factors that have often been overlooked or insufficiently investigated so far. This study advances surface engineering for Zn anodes and introduces interfacial mechanics as a design parameter for durable artificial protective layers in aqueous battery systems.