A Sulfolane-Based Electrolyte Optimized for Microporous Activated Carbon-Sulfur Composites for Lithium Sulfur Batteries

Abstract

The dissolution of lithium polysulfide into electrolytes is a major limitation of Li-S batteries that hinders their practical applications. Lithium polysulfide dissolution is suppressed by using sulfur-complexed microporous-carbon cathodes in lithium–sulfur batteries. This study reports the use of a localized high-concentration electrolyte (LHCE), in which a sulfolane (SL) high-concentration electrolyte is diluted with hydrofluoroether (HFE), for the strong suppression of lithium polysulfide elution. A previously reported sulfolane electrolyte in the solvated state exhibits a short cycle life of eight cycles, whereas the sulfur-containing microporous-carbon cathode with a sulfolane-based electrolyte prepared in the ratio of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) : SL : HFE = (0.572–0.953) : 2.00 : 1.26 (mol) exhibits a discharge capacity of more than 550 mAh g−1, even after 50 charge–discharge cycles. Increasing the LiTFSI ratio decreases the response current during discharge, as indicated by cyclic voltammetry. A sulfur cathode with microporous carbon (AZC) shows equivalent performance on decreasing the amount of solvated LiTFSI. This study could guide the design and development of electrolytes for sulfur-containing microporous-carbon cathodes.