In Situ Investigations of the Interfacial Reactions at Cathodes in Solid-State Lithium-Oxygen Batteries: Challenges and Advances

ABSTRACT Solid-state lithium-oxygen (Li-O 2 ) batteries are considered promising next-generation energy storage systems due to their high theoretical energy density and improved safety. However, their practical application remains limited by sluggish interfacial reaction kinetics and inadequate cycling stability, suggesting that current materials and interfacial architectures have yet to achieve their full potential. This Perspective first elucidates the fundamental mechanisms governing Li-O 2 interfacial reactions, highlighting critical insights derived from advanced in situ characterization methodologies. Building on these mechanistic foundations, we present strategic approaches for the rational design of efficient triple-phase interfaces involving the electrode, solid-state electrolyte, and O 2 . Furthermore, we evaluate how external fields, such as light or magnetic fields, can be integrated to accelerate reaction kinetics. Finally, we identify major scientific challenges and suggest future research directions focused on interface stabilization and multi-scale engineering, aiming to overcome existing kinetic barriers and advance high-performance solid-state Li-O 2 batteries.