We have determined saturated solubility of Li2Sm and S8 in various type of electrolytes ranging from molecular solvents to aprotic and solvate ionic liquids to study factors that govern the dissolution of S8 and Li2Sm species into electrolyte. In terms of solvent parameters, the solubility of Li2Sm was well correlated with Gutmann’s donor number, whereas solubility of S8 was explained by Hildebrand solubility parameter. Although weakly coordinating solvents having low donor number could greatly suppressed dissolution of Li2Sm, supporting lithium salts (e.g., LiTFSA) were hardly soluble in such weakly coordinating solvents. An exception was ionic liquid-based electrolytes: ionic liquids having a weakly coordinating anion can dissolve the supporting salt while suppressing dissolution of Li2Sm. We show how the electrolyte properties of the ionic liquids link to the cell performance such as large capacity, high Coulombic efficiency, and good reversibility.
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