Lithium-Sulfur Batteries with Micelle-Structured Electrolytes and Imide-Based Salts

Imide electrolytesalts have received increasing interest in lithium-sulfurbattery (LSB) research due to their oxidation capacity, thermal stability,and cycling stability. Although the ionic conductivity of imide electrolytesis moderate, a LSB with imide electrolyte salts exhibits improvedcharge-discharge (CD) cycling capacity and Coulombic efficiency.Here, we applied an effective strategy to suppress polysulfide dissolutionby using a micelle-structured fluorinated ether-based additive (F4EO2) with lithium bis(trifluorosulfonyl)imide (LiTFSI)and lithium bis(fluorosulfonyl)imide (LiFSI) electrolyte salts. Incontrast to the LiFSI electrolyte, the LiTFSI imide electrolyte withF(4)EO(2) additive shows a superior performancein terms of its compatibility with the lithium (Li)-metal anode, electrochemicalstability, cycling stability, and high specific discharge capacityof ca. 1331 mAh/g using the sulfur/carbon (S/C) composite//electrolyte//Li-metalbattery configuration at 0.1C. The LSB performance is enhanced withan increase of the concentration of the F4EO2 additive in the electrolyte solution. The results demonstrate thatthe electrolyte solution with the F4EO2 additiveand LiTFSI salt improves the LSB performance by suppressing polysulfidedissolution and forming a favorable passivation layer on the Li-metalanode, leading to a specific discharge capacity of ca. 1221 mAh/gafter 20 cycles and 950 mAh/g after 100 cycles (for T5FDLiTFSI), respectively,with a Coulombic efficiency of ca. 99.98% and 99.99% after 20 and100 CD cycles, respectively.