Fluorinated Ether Based Electrolyte for High-Energy Lithium–Sulfur Batteries: Li⁺ Solvation Role Behind Reduced Polysulfide Solubility

Abstract

By employing new electrolytes, the polysulfide shuttle phenomenon, one of the main problems of lithium-sulfur (Li-S) batteries, can be significantly reduced. Here we present excellent Coulombic efficiencies as well as adequate performance of high-energy Li-S cells by the use of a fluorinated ether (TFEE) based electrolyte at low electrolyte loading. The observed altered discharge profile was investigated both by electrochemical experiments and an especially tailored COSMO-RS computational approach, while the details of the discharge mechanism were elucidated by two operando techniques: XANES and UV-vis spectroscopy. A significant decrease of polysulfide solubility compared to tetraglyme is due to different Li+ solvation mode.