Atomic Layer Deposition of Li _x Al _y S Solid-State Electrolytes for Stabilizing Lithium-Metal Anodes

Abstract Increasing global demands for energy storage in electric vehicles and the grid necessitate “beyond‐lithium‐ion” batteries that simultaneously exhibit high capacity, long‐term cyclability, and excellent safety. Several candidates, most notably lithium–air and lithium–sulfur batteries, utilize lithium‐metal anodes. Although the specific capacity of lithium metal is unrivaled (3860 mA h g −1 ), the capacity fade and risk of catastrophic failure must be overcome. Herein, we describe ultrathin, ionically conducting lithium aluminum sulfide (Li x Al y S) coatings prepared on lithium‐metal anodes by using atomic layer deposition, which stabilize the Li–electrolyte interface and reduce (up to five times) the interfacial impedance of lithium–metal anodes in contact with organic electrolyte. We demonstrate that these thin films effectively suppress dendrite formation and preserve a smooth, low‐surface‐area morphology for electrodeposited lithium metal, thereby doubling the lifetime of Li–Cu asymmetric cells.