Accelerating Lithium‐Ion Transfer and Sulfur Conversion via Electrolyte Engineering for Ultra‐Stable All‐Solid‐State Lithium–Sulfur Batteries

Abstract Offering ultrahigh energy density and exceptional safety, all‐solid‐state lithium–sulfur batteries (ASSLSBs) can be one of the most promising energy storage systems if their inherent challenges, including slow Li⁺ mass transport and insufficient sulfur utilization efficiency, are completely tackled. In this work, an amide‐based electrolyte additive with a high Gutmann donor number is used to construct a deep eutectic system, a “one‐stone‐two‐birds” solution to address these issues. In particular, an acetamide is used to interact with the insulative Li₂S via a strong S─H bond and Li─O bond to boost the electrochemical reaction kinetics of lithium‐sulfur (Li─S) chemistry and sulfur utilization and simultaneously form a deep eutectic LiTFSI‐acetamide system to enhance ionic conductivity of solid polymer electrolytes (SPEs). Such a seamless integration of this system into the solid‐state LSBs helps deliver a high initial discharge specific capacity of 1012 mAh g⁻¹ at 0.05 C and attain a stable cyclability for 1300 cycles at 0.1 C. This remarkable achievement in high performance and stability can effectively facilitate the commercialization of ASSLSBs.