Interfaces in All-Solid-State Li Metal Batteries: From Fundamental Research to Practical Applications

All-solid-state Li-metal batteries (ASSLMBs) are promising for next-generation energy storage due to their high energy density and enhanced safety. However, their commercialization remains constrained by complex interfacial phenomena that critically govern the electrochemical performance and durability. In this Review, we present a comprehensive and integrated overview of interfacial science in ASSLMBs, spanning both fundamental studies and practical developments. We begin with a general introduction to typical and state-of-the-art solid-state electrolytes (SEs), followed by a detailed discussion of key interfacial challenges, including the Li anode/SEs interface, the cathode/SEs interface, and internal interfaces within the SEs. Strategies developed to address these issues were critically evaluated and compared. Further, advanced characterization techniques and computational simulations are then examined as essential tools to probe, diagnose, and understand the interfacial evolution. Most importantly, from an interface-centered perspective, we highlight recent progress in safety, electrochemical performance, scalability, and cost effectiveness, helping to bridge the gap between laboratory research and real-world applications. Finally, we provide our forward-looking insights into future research directions aimed at accelerating the commercialization of the ASSLMBs.