The Electrochemical Society, Journal of The Electrochemical Society, 7(167), p. 070528, 2020
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Various organic compounds were investigated as co-solvents in an ionic liquid (IL), N,N-butylmethyl pyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI), based electrolyte for Li-S batteries. For the Pyr14TFSI/Co-solvent binary system, only 1,3-dioxolane (DOL) afforded stable cycling performance with reasonable Coulombic efficiency (CE). Further increase in DOL concentration leads to a higher initial capacity but deteriorated CE. In an attempt to balance CE and capacity, 2.0 M LiTFSI Pyr14TFSI/DOL (2:1) exhibited optimal performance in terms of initial discharge capacity of 896 mAhg−1 and CE of 98.1% for over 200 cycle. The role of DOL and salt concentration interplay in the binary electrolyte was simulated by ab-initio molecular dynamics (AIMD). The solvation energy with varying co-solvent and LiTFSI salt concentration provides useful information when looking toward implementing other IL-based electrolyte systems for Li-S chemistry.