A facile synthesis of high-surface-area sulfur-carbon composites for Li/S batteries
Small-grained elemental sulfur is precipitated from sodium thiosulfate (Na2S2O3) in a carbon-containing oxalic acid (HOOC-COOH) solution through a novel spray precipitation method. Surface area analysis, elemental mapping, and transmission electron micrographs revealed that the spray-precipitated sulfur particles feature 11 times higher surface area compared to conventional precipitated sulfur, with homogeneous distribution in the carbon. Moreover, the scanning electron micrographs show that these high-surface-area sulfur particles are firmly adhered to and covered by carbon. This precipitated S-C composite exhibits high discharge capacity with about 75% capacity retention. The initial discharge capacity was further improved to 1444mAhg-1 by inserting a free-standing single-walled carbon nanotube layer in between the cathode and the separator. Moreover, with the help of the fixed capacity charging technique, 91.6% capacity retention was achieved.