Balancing Anodic Stability and Cathodic Kinetics in Practical Lithium-Sulfur Batteries With Non-fluorinated Weakly Solvating Solvents

The performance of lithium-sulfur (Li-S) batteries is crucially affected by the anodic stability of Li-metal and cathodic conversion kinetics of sulfur-carbon (S/C) composites. Herein, a weakly solvating electrolyte (WSE) with moderate lithium polysulfides (LiPSs) solubility, consisting of 1 M lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) in non-fluorinated solvent of cyclopentyl methyl ether (CPME) and 1,3-dioxolane (DOL) additive, is employed in Li-S batteries to simultaneously achieve high anodic stability and appropriate cathodic kinetics. This WSE exhibits a good capability of suppressing LiPSs shuttling by forming an anions-dominated Li + solvation structure, effectively inducing a stable solid electrolyte interphase (SEI) to guarantee anodic stability of the Li-metal anode. Additionally, the DOL additive in the WSE aids in forming a thin organic-inorganic hybrid cathode electrolyte interphase (CEI) on the surface of S/Li 2 S particles, which maintains good conversion kinetics and suppresses dead S/Li 2 S growth in the S/C cathode. Consequently, Li-S batteries with the WSE deliver a high initial capacity (≈1208 mAh g −1 ), a high average Coulombic efficiency (≈98.6%), and a high capacity retention rate (≈82.4%) over 200 cycles. Stable cycling performance over 100 cycles is also observed in the Li-S pouch cell with the WSE even under harsh conditions.