Tailoring Terminal Groups in Sulfonyl Solvents to Boost Compatibility with Lithium Metal Anodes

Abstract

Sulfonyl-based compounds are considered promising electrolyte solvents because of their high dielectric constant, excellent anodic stability, and non-flammability. However, their use in Li metal batteries (LMBs) is limited by the incompatibility with Li, causing unstable interfacial chemistry and dendrite growth. Herein, we designed an N,N-dimethylsulfamoyl fluoride (DMSF) electrolyte by functionalizing a fluorosulfonyl (FSO2–) core with an N,N-dimethyl terminal group, enabling the LMB with enhanced cycling stability and energy density. The increased steric hindrance in DMSF with methylation weakens the interaction with Li ions, resulting in a structure that is weakly solvating and exhibits fast ion transport kinetics. Methylation also facilitates the decomposition of DMSF, leading to the formation of a rich LiF/Li2S hybrid solid electrolyte interphase that suppresses interfacial side reactions. Consequently, the 4.5 V-charged 50 μm Li||LiNi0.8Co0.1Mn0.1O2 (4 mAh cm–2) cells exhibit stable cycling (80% capacity retention for 850 cycles), 5 C fast charging, and a wide operating temperature range (–50~60 °C). Moreover, a 5-Ah pouch cell employing DMSF delivers an energy density of 540 Wh kg–1 and exhibits high stability over 110 cycles. This study establishes terminal group modification as a crucial advance for enabling compatible sulfonyl-based electrolytes in high-performance LMBs.