Abstract Carbonate‐electrolyte‐based lithium–sulfur (Li–S) batteries with solid‐phase conversion offer promising safety and scalability, but their reversible capacities are limited. In addition, large‐format pouch cells are paving the way for large‐scale production. This study demonstrates the in situ formation of a solid‐electrolyte interphase (SEI) as a protective layer using vinylene carbonate (VC), highlighting its industrial adaptability. A high reversible capacity is achieved by the lithiated poly‐VC SEI formed inside the cathode particles as a nanoscale ionic conduction path, along with the traditional surface protective layer. Furthermore, the severe dissolution of poly‐VC is mitigated by LiF derived from fluorine ethylene carbonate as a co‐solvent, enabling high rate performance and a long cycle life. A large 8 Ah pouch cell is successfully developed, which shows a high energy density of 400 Wh kg−1 based on the cell weight. This work demonstrates the high performance of large‐scale Li–S batteries with the in situ formation of a protective layer as a scalable technique for future applications.
