Organosulfide‐Based Deep Eutectic Electrolyte for Lithium Battery

Deep eutectic electrolytes (DEEs) are a new class of electrolytes with unique properties. However, the intermolecular interactions of DEEs are mostly dominated by Li···O interactions, limiting the diversity of chemical space and material constituents. Herein, we report a new class of DEEs induced by Li···N interactions between 2,2'-dipyridyl disulfide (DpyDS) and lithium bis(trifluoro-methanesulfonyl)imide (LiTFSI). The strong ion-dipole interaction triggers the deep eutectic phenomenon, thus liberating the Li + from LiTFSI and endowing the DEEs with promising ionic conductivity. These DEEs show admirable intrinsic safety, which cannot be ignited by flame. The DEE at the molar ratio of DpyDS:LiTFSI = 4:1 (abbreviated as DEE-4:1) is electrochemically stable between 2.1 and 4.0 V vs. Li/Li + , and exhibits an ionic conductivity of 1.5 × 10 -4 S cm -1 at 50 oC. The Li/LiFePO 4 half cell with DEE-4:1 can provide a reversible capacity of 130 mAh g -1 and Coulombic efficiency above 98% at 50 oC.