Preparation of three-dimensional hybrid nanostructure-encapsulated sulfur cathode for high-rate lithium sulfur batteries

A three-dimensional hybrid nanostructure incorporating the merits of the MWCNTs webs (MWCNTs-W) and the reduced graphene oxide (RGO) is designed to improve the high-rate cycling performance of the lithium-sulfur batteries. Owing to the excellent Li ion and electronic transport properties of the MWCNTs-W and the RGO, this unique structure can provide a three-dimensional conductive network and promote rapid charge-transfer reaction at the cathode. Furthermore, because of the rough surface and porous structure of the MWCNTs after activation with KOH, and the special adsorption ability of the RGO, the soluble polysulfide intermediates can be effectively trapped in the cathode. Therefore, when evaluating the electrochemical properties of the RGO@MWCNTs-W/S composite as the cathode material for lithium-sulfur batteries, it exhibits an excellent cyclical stability and high rate performance. In particular, even at an ultrahigh rate (5 C), a discharge capacity as high as 620 mAh g is still retained for the RGO@MWCNTs-W/S composite with 68.93 wt% sulfur after 200 cycles, and the average coulombic efficiency is 96%

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 m g) and a high inner pore volume (1.31 cm g). 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 after 180 cycles at 0.2 C. At a higher rate of 1 C, the capacity stabilizes at 666.0 mAh g 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

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