Simple Realization of a Novel Metal–Metal Composite Solid Solution and Its Potential Application as a Current Collector

Abstract Solid‐solution‐based metal alloy phases are an important phase category and effective structural control method. Nevertheless, Hägg's rule retards the formation of metal−metal composite solid solution (CSS); consequently, there is a lack of understanding regarding its properties and potential applications. Herein, as a proof‐of‐concept study, a novel Cu–0.01 wt.% Ag CSS with a unique atomic structure containing both interstitial and substitutional Ag atoms in the Cu lattice is synthesized via a nonequilibrium method. When used as current collectors in Li||CSS metal cells, the CSS can significantly reduce the nucleation overpotential, improve the average Coulombic efficiency (CE) and cycle life, and mitigate uncontrolled Li dendrite deposition compared with Li||Cu cells. Noble metals are often used for interface modification of electrode materials, yet large‐scale applications require convenient and precise control of their content. Here, only a negligible Ag content is required, which, to the best of current knowledge, is almost the lowest noble metal content reported to date. The results provide new insights into the design and application of novel alloy phases such as lithium metal batteries.