Probing Electronic Structures With Ultraviolet Photoelectron Spectroscopy (UPS): Insights for Advanced Lithium‐Based Battery Systems

ABSTRACT The pursuit of higher energy density and safety drives the development of next‐generation lithium‐based batteries, including Li metal, Li‐S, and all‐solid‐state batteries. These advanced technologies face challenges from complex electronic structure and interfacial charge transfer, which can be effectively studied using ultraviolet photoelectron spectroscopy (UPS). As a powerful surface‐sensitive technique, UPS measures key electronic parameters such as work function, ionization energy, and valence band structure. This review provides a comprehensive and timely overview of UPS applications in lithium‐based batteries. Following an introduction to its fundamentals, emphasis is placed on how UPS‐derived insights elucidate intrinsic electronic structures, ion storage mechanisms, interfacial reactions, and guide material modifications and the design of artificial interphases in various lithium‐based batteries. Key challenges in applying UPS to battery research are also summarized, including reliable spectral acquisition, accurate data interpretation, and the fundamental gap between idealized model systems studied under ultrahigh vacuum and real battery operating conditions. Finally, future perspectives emphasize the establishment of unified protocols, deeper integration with theoretical computations, and the development of operando UPS capabilities to accelerate the design of next‐generation high‐performance rechargeable batteries.