Electrochemical Properties of Sulfurized Polyacrylonitrile with High Sulfur Content for Lithium/Sulfur Batteries

Sulfur composites with differing sulfur levels were prepared by heating sulfur and polyacrylonitrile. Composites with 22 and 39 wt% sulfur show a single phase of sulfurized polyacrylonitrile, while those with higher sulfur contents of 53 and 65 wt% have an additional phase corresponding to elemental sulfur. Their elemental sulfur contents were 16 and 27 wt%, respectively. In lithium/sulfur batteries, the composite with 65 wt% sulfur shows poor capacity due to preferential reaction of elemental sulfur. The composite affords a first discharge capacity of 175 mAh g(-1)-cathode and cannot charge reversibly. However, the composite with 53 wt% sulfur can charge reversibly with a high capacity of 429 mAh g(-1)-cathode at the 50th cycle, which is higher than that of the 39 wt% composite. These results indicate that an appropriate amount of elemental sulfur can have a positive effect on electrochemical properties of sulfurized polyacrylonitrile.