Flower-Shaped Sulfurized Polyacrylonitrile Nanostructures as Cathode Materials for High-Performance Lithium–Sulfur Batteries

Sulfurized polyacrylonitrile (SPAN) is considered one of the most promising cathode materials for lithium–sulfur (Li–S) batteries due to its benign sulfur utilization, good cycling stability, and high Coulombic efficiency. However, the insufficient sulfur content and sluggish reaction kinetics greatly limit its practical energy density and rate performance. Here, a novel three-dimensional (3D) flower-shaped SPAN (SPAN-F) composite is designed to simultaneously address the above-mentioned issues. Specifically, the thin PAN nanopetals can provide more abundant active sites for the sulfurization reaction, enabling a more saturated sulfur content. In addition, the unique flower-shaped nanostructure is conducive to transporting Li+ and adapting to volume variation during the lithiation/delithiation processes of Li–S batteries. Consequently, the SPAN-F3 cathode exhibits a large reversible capacity of 789 mA h g–1composite at 0.2C, a superb rate capability up to 4C, and an ultralong cycle life of more than 500 cycles. Moreover, the thick cathodes with a high mass loading of 8.6 mg cm–2 maintain excellent electrochemical performances under lean electrolyte (E/SPAN = 5.0 μL mg–1) conditions, showing tremendous potential for practical applications. This investigation reinforces the importance of controlling particle structure for electrode materials and provides a promising solution toward practical Li–S batteries.