Anion-Rich Interface via a Self-Assembled Monolayer toward a Long-Lifespan Li Metal Battery

Due to the extremely high energy density of Li metal, Li metal batteries are regarded as one of the most promising candidates for next-generation energy storage systems. However, interfacial issues, particularly the unstable solid electrolyte interphase (SEI) and lithium dendritic growth, hinder practical application. Herein, we induce an anion-rich interface near the Li metal by introducing positively charged self-assembled monolayers (SAMs) on ceramic-coated separators to simultaneously stabilize the SEI and homogenize the Li deposition. The anion-rich interface, originating from the electrostatic attraction of SAMs, promotes the preferential decomposition of salt anions over organic solvent molecules, leading to the formation of a stable anion-derived inorganic component, notably LiF. Furthermore, the positively charged SAMs immobilize anions, significantly mitigating dendritic Li by improving the Li⁺ transference number (∼0.73) and thereby mitigating dendritic Li growth. Hence, we present SAMs on ceramic-coated separators as an innovative way to improve the long-term cycling performance of Li metal batteries.