Anode Interfacial Issues in Solid‐State Li Batteries: Mechanistic Understanding and Mitigating Strategies

All‐solid‐state Li metal batteries (ASSLBs) using inorganic solid electrolyte (SE) are considered promising alternatives to conventional Li‐ion batteries, offering improved safety and boosted energy density. While significant progress has been made on improving the ionic conductivity of SEs, the degradation and instability of Li metal/inorganic SE interfaces have become the critical challenges that limit the coulombic efficiency, power performance, and cycling stability of ASSLBs. Understanding the mechanisms of complex/dynamic interfacial phenomena is of great importance in addressing these issues. Herein, recent studies on identifying, understanding, and solving interfacial issues on anode side in ASSLBs are comprehensively reviewed. Typical issues at Li metal/SE interface include Li dendrite growth/propagation, SE cracking, physical contact loss, and electrochemical reactions, which lead to high interfacial resistance and cell failure. The causes of these issues relating to the chemical, physical, and mechanical properties of Li metal and SEs are systematically discussed. Furthermore, effective mitigating strategies are summarized and their effects on suppressing interfacial reactions, improving interfacial Li‐ion transport, maintaining interfacial contact, and stabilizing Li plating/stripping are highlighted. The in‐depth mechanistic understanding of interfacial issues and complete investigations on current solutions provide foundations and guidance for future research and development to realize practical application of high‐performance ASSLB.