Improved dischargeability and reversibility of sulfur cathode in a novel ionic liquid electrolyte

A novel room temperature ionic liquid (N-methyl-N-butyl-piperidinium bis(trifluoromethanesulfonyl) imide (PP14-RTIL) ) was synthesized and tested as electrolyte for Li/S cells. The CV results revealed that this new RTIL electrolyte has a wide potential window of 5.2 V ∼ −0.15 (vs. Li/Li+), and is electrochemically stable and workable for lithium and sulfur electrodes. The charge–discharge experiments of Li/S cells using the PP14- RTIL electrolyte demonstrated that the sulfur cathode can achieve a high initial capacity of 1055 mAh/g and maintains a reversible capacity of ca. 750 mAh/g after a few of cycles, showing a greatly improved dischargeability and cycleability as compared with the sulfur cathodes cycled in organic liquid or polymer electrolytes.