Sulfur‐Embedded Activated Multichannel Carbon Nanofiber Composites for Long‐Life, High‐Rate Lithium–Sulfur Batteries

Abstract

Despite the 3–5 fold higher energy density than the conventional Li‐ion cells at a lower cost, commercialization of Li–S batteries is hindered by the insulating nature of sulfur and the dissolution of intermediate polysulfides (Li 2 S X , 4 < X ≤ 8) into the electrolyte. The authors demonstrate here multichannel carbon nanofibers that are composed of parallel mesoporous channels connected with micropores as sulfur containment. In addition, hydroxyl functional groups are formed on the carbon surface through a chemical activation to enhance the interaction between sulfur and carbon. In the sulfur embedded composite, the mesoporous multichannel enhances the active material utilization and sulfur loading, while the micropores act as a reaction chamber for sulfur component and trap site for polysulfide with the assistance of the functional groups. This sulfur–carbon composite electrode with 2.2 mg cm −2 sulfur displays excellent performance with high rate capability (initial capacity of 1351 mA h g −1 at C/5 rate and 847 mA h g −1 at 5C rate), maintaining 920 mA h g −1 even after 300 cycles (a decay of 0.07% per cycle). Furthermore, a stable reversible capacity of as high as ≈1100 mA h g −1 is realized with a higher sulfur loading of 4.6 mg cm −2 .