Anode-free lithium metal batteries represent a promising pathway to higher energy density, but their success depends critically on stable current-collector interfaces where lithium deposition initiates. Traditional copper foils suffer from native oxide layers that degrade performance and enable parasitic side reactions. A new ion-implantation strategy addresses this fundamental challenge by creating atomically clean, oxidation-resistant copper surfaces without increasing collector thickness.
The technique works by implanting copper ions directly into commercial copper foils, which simultaneously removes the native oxide layer and generates subsurface vacancy clusters just beneath the surface. These atomic-scale defects function as oxygen traps, preventing reoxidation during battery operation and significantly enhancing interfacial conductivity. Computational simulations combined with experimental validation demonstrate that the vacancy clusters fundamentally alter interfacial chemistry in ways that traditional surface treatments cannot achieve.
When applied in anode-free lithium metal cells, these engineered collectors enable formation of an ultrathin, lithium oxide-enriched solid electrolyte interphase that promotes uniform lithium deposition across the electrode surface. This uniform distribution is essential because localized deposition leads to dendritic growth, short circuits, and rapid capacity fade. The improved interfacial control suppresses parasitic side reactions that typically consume electrolyte and active lithium.
Laboratory results demonstrate the practical benefits: the engineered current collectors sustained 600 charge-discharge cycles with 98.8% Coulombic efficiency under lean-electrolyte conditions—a demanding test that reflects real-world operating constraints. This stability exceeds conventional copper collectors by a substantial margin and indicates that the interface modifications remain effective throughout extended cycling.
The findings establish ion implantation as a scalable, thickness-neutral method for atomic-scale interface engineering. Since the technique modifies only the surface chemistry without bulk material addition, it can be integrated into existing copper foil manufacturing processes. This compatibility with current production methods is crucial for eventual commercialization of advanced lithium metal batteries across automotive and energy storage applications.
