Functionalized n-doped porous carbon nanofiber webs for a lithium-sulfur battery with high capacity and rate performance

Functionalized N-doped porous carbon nanofiber webs/sulfur (N-PCNF/S) composites are first proposed as the cathode materials for an advanced lithium-sulfur battery. The functionalized N-doped porous carbon nanofiber webs (N-PCNF) with an appropriate N doping (4.32 wt %) are synthesized by a facile approach, which consists of pyrolyzation of polypyrrole nanofiber and a subsequent KOH activation. Instrumental analysis shows that N-PCNF possesses a large specific surface area (2642 m² g^-1) and a high inner pore volume (1.31 cm³ g^-1). When evaluating its electrochemical properties in a lithium-sulfur battery, the N-PCNF/S composite with 77.01 wt % sulfur content displays an excellent electrochemical performance. The specific discharge capacity still reaches 749.8 mAh g ^-1 after 180 cycles at 0.2 C. At a higher rate of 1 C, the capacity stabilizes at 666.0 mAh g^-1 after 200 cycles. This work demonstrates that combining the favorable aspects of N doping modification and one-dimensional nanostructure in the carbon matrix design is an effective way to improve the electrochemical performance of the carbon/sulfur cathodes.