High-Density Ultrafine Nucleation on Discontinuous Residual Ag Suppresses Localized Growth for Stable Lithium Metal Deposition

Lithium metal batteries are promising next-generation energy storage systems due to the exceptionally high theoretical capacity and low redox potential of lithium metal. However, their practical application remains limited by nonuniform lithium deposition, which leads to low Coulombic efficiency and severe safety concerns. Such instability is closely related to heterogeneous lithium nucleation on conventional copper (Cu) substrates. Herein, we introduce an interfacial design strategy using discontinuous residual Ag uniformly distributed on a wrinkled Cu substrate with dominant [100] facets, without forming aggregated particles or discrete nucleation seeds. The crystallographically uniform Cu [100] surface provides a homogeneous interfacial environment for Li nucleation, while the discontinuous residual Ag further lowers the nucleation barrier without creating isolated dominant growth centers. The residual Ag modulates the Cu-Li interfacial interaction, enabling spatially uniform nucleation across the surface. Electrochemical measurements reveal a reduced nucleation overpotential on the Ag/Cu substrate compared to bare Cu. Ex-situ SEM shows the formation of high-density ultrafine lithium nuclei that are preserved during deposition and undergo lateral coalescence rather than localized vertical growth. Notably, this system exhibits a prolonged nucleation-dominated deposition regime, which delays the transition to growth-dominated behavior. This kinetic pathway shift leads to compact, dendrite-free lithium deposition at practical areal capacities. This work demonstrates that controlling the nucleation-to-growth transition through interfacial modulation provides an effective strategy for regulating lithium deposition behavior. The proposed approach establishes a mechanistic framework for stabilizing lithium metal anodes without relying on thick coatings or discrete lithiophilic particles.