High-Performance Lithium-Sulfur Batteries Based on Ionic-Liquid Electrolytes with Bis(fluorolsufonyl)imide Anions and Sulfur-Encapsulated Highly Disordered Activated Carbon

Composite sulfur-carbon electrodes were prepared by encapsulating sulfur into the micropores of two types of activated carbons, nano-sized carbon BP2000 and micrometer-sized carbon. The galvanostatic cycling performance of the obtained electrodes was studied in 0.5 M lithium bis(trifluoromethylsulfonyl)imide (Li TFSI) in 1-methyl-1-butylpyrrolidinium TFSI (BMP TFSI), 0.5 M Li TFSI in 1-methyl-1-butylpyrrolidinium bis(fluorosulfonyl)imide (MPP FSI), and 0.5 M Li bis(fluorosulfonyl) imide (FSI) in MPP FSI ionic-liquid (IL) electrolyte solutions. It is shown that the performance of Li-S cells is achieved by matching the IL anion, the morphology and structure of the carbon matrices, and the sulfur loading. High-performance of Li-S cells, with composite Li-S cathodes prepared with micrometersized activated carbon in IL electrolyte with FSI anions, are demonstrated at 60 degrees C. After 48 cycles, the discharge capacity of the cells approaches a value of 1235 mAhg(-1) with acycling efficiency of about 100 %.