Ultrathin Yet Effective: 90 nm ZnF2 Layer for Stabilizing Zinc–Metal Anodes

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 ZnF₂ 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 ZnF₂-coated Zn achieved lifespans of 1500 h at 0.5 mA cm^–2 and 500 h at 3.0 mA cm^–2. Full cells with Mn_xV₂O₅ cathodes retained 82% capacity after 2000 cycles. Crucially, nanoscratch tests revealed that the optimum thickness of ZnF₂ films provided reasonable interfacial toughness, offering new insights into the mechanical–electrochemical codesign 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.