Lithium/sulfur (Li/S) batteries using the novel perfluorinated ionomer electrolyte with lithium sulfonyl dicyanomethide functional groups as both separator and electrolyte are demonstrated. Comparison was made with the Li/S batteries with the conventional liquid electrolyte, poly(vinylidenefluoride-hexafluoropropylene) [P(VDF-HFP)] gel polymer electrolyte, the lithiated Nafion ionomer electrolyte, and the novel perfluorinated ionomer electrolyte. The battery with novel perfluorinated ionomer electrolyte shows stable capacity retention compared with the batteries with the conventional liquid electrolyte and the gel electrolyte, and good rate performance compared with the battery with the lithiated Nafion ionomer electrolyte.