Hydrofluoroether Diluted Dual‐Salts‐Based Electrolytes for Lithium‐Sulfur Batteries with Enhanced Lithium Anode Protection

Abstract With a high energy density, lithium–sulfur batteries (LSB) are regarded as one of the promising next‐generation energy storage systems. However, many challenges hinder the practical applications of LSB, such as the dendrite formations/parasitic reactions on the Li metal anode and the “shuttle effect” of lithium polysulfides of the LSB cathode. Herein, a novel diluted medium‐concentrated electrolyte (DMCE) is developed by adding 1,1,2,2‐tetrafluoroethyl 2,2,3,3‐tetrafluoropropyl ether (TTE) into a dual salt medium‐concentrated electrolyte (MCE) consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)–lithium bis(fluorosulfonyl)imide (LiFSI)/tetrahydrofuran (THF)–dipropyl ether (DPE). The optimized DMCE electrolyte is capable of protecting the Li metal anode and suppresses the dissolution of polysulfides and the “shuttle effect”, delivering a high coulombic efficiency (CE) of Li plating–stripping up to 99.6% even at a low concentration of Li salt (1.0–2.0 m ). Impressively, compared with the cells cycled in the MCE electrolyte, the LiS cells with the DMCE‐2.0 m electrolyte have delivered an enhanced initial capacity of 682 mAh g −1 with an excellent capacity retention of 92% for 500 cycles. This strategy of using fluorinated ether as diluent solvent in a medium‐concentrated electrolyte can accelerate the commercialization of LSB.