The paper "Quantifying Inactive Lithium in Lithium Metal Batteries" by Chengcheng Fang et al. addresses the issue of inactive lithium (Li) formation, which is a major cause of capacity loss and safety hazards in lithium metal batteries (LMBs). The authors introduce a novel analytical method, Titration Gas Chromatography (TGC), to accurately quantify the amount of unreacted metallic Li⁰, which is often overlooked in previous studies. They find that metallic Li⁰, rather than the electrochemically formed solid electrolyte interphase (SEI), is the primary contributor to capacity loss. Using cryogenic electron microscopy, they further reveal that metallic Li⁰ is surrounded by insulating SEI, losing its electronic conductive pathway to the bulk electrode. The study also proposes strategies to mitigate the formation of inactive Li⁰, such as controlling the microstructure of the plated Li deposits and applying external pressure to maintain a good structural connection. These findings provide a comprehensive understanding of the mechanisms leading to capacity decay in LMBs and offer potential solutions for improving their performance.The paper "Quantifying Inactive Lithium in Lithium Metal Batteries" by Chengcheng Fang et al. addresses the issue of inactive lithium (Li) formation, which is a major cause of capacity loss and safety hazards in lithium metal batteries (LMBs). The authors introduce a novel analytical method, Titration Gas Chromatography (TGC), to accurately quantify the amount of unreacted metallic Li⁰, which is often overlooked in previous studies. They find that metallic Li⁰, rather than the electrochemically formed solid electrolyte interphase (SEI), is the primary contributor to capacity loss. Using cryogenic electron microscopy, they further reveal that metallic Li⁰ is surrounded by insulating SEI, losing its electronic conductive pathway to the bulk electrode. The study also proposes strategies to mitigate the formation of inactive Li⁰, such as controlling the microstructure of the plated Li deposits and applying external pressure to maintain a good structural connection. These findings provide a comprehensive understanding of the mechanisms leading to capacity decay in LMBs and offer potential solutions for improving their performance.