Preparation of Li–Mg Thin Films by Vacuum Deposition Process and Their Application in All-Solid-State Batteries

All-solid-state lithium metal batteries have attracted significant attention as next-generation batteries with the potential to achieve substantial performance improvements over conventional lithium-ion batteries.However, achieving a higher energy density requires not only improving the performance of the Li metal anode but also overcoming the challenges posed by a thinner, lighter configuration.In this study, a vacuum deposition process is employed to prepare thin Li-Mg films with thicknesses of several micrometers, which are difficult to achieve using conventional processes.Subsequently, the electrochemical properties of these thin films are evaluated in all-solid-state lithium metal batteries, and the functional role of Mg is investigated.The results reveal that the cycle life is highly dependent on the Mg content.Specifically, the Li (5 m)-Mg (400 nm) configuration (~7 at% Mg) exhibits the highest performance, achieving 87.7 % capacity retention after 100 cycles.Crosssectional observations confirm uniform alloying of the prepared film.Furthermore, the optimal film exhibits a stable interface with the solid electrolyte (Li6PS5Cl), effectively suppressing void formation during repeated plating/stripping cycles.This improved cycling stability is attributed to increased elastic modulus of the films, and the suppression of void formation, which is facilitated by the improved wettability induced by Mg.