Perfluorosulfonic Acid Membrane for Lithium–Sulfur Batteries with S/C Cathodes

Polymer electrolyte based on Nafion-117 membranes in the Li+ form with intercalated 1,3-dioxolane-dimethoxyethane solvent mixtures (DOL-DME) has been obtained. The obtained electrolyte Nafion-Li+-DOL-DME has been characterized by DSC analysis, IR- and impedance spectroscopy. The solvent uptake of membrane in the DOL-DME mixture amounts to 1.9. Nafion-Li+-DOL-DME is characterized by an ionic conductivity ~10−7 S cm−1 at room temperature. The comparative study of the electrochemical properties of Li–S batteries with liquid electrolyte (1M Li(CF3SO2)2N in DOL-DME) with polypropylene film (PP) or Nafion-Li+-DOL-DME and S/C composites with mesoporous carbon as cathode materials has shown that the use of membrane can improve cyclability of the cell. The first-cycle discharge capacities of S/C electrodes in the Li–S battery cells with PP and Nafion-Li+-DOL-DME were 730 and 450 mAh g−1, respectively (0.1 mV s−1). However, the discharge capacity of S/C in the cell with PP reduced significantly after 10 cycles. The Li–S battery with the use of membrane exhibits significantly enhanced cyclability. The discharge capacity of S/C in the cell with Nafion-Li+-DOL-DME amounts to 365 mAh g−1 after 10 cycles and to up to 290 mAh g−1 after 40 cycles.