A novel sulfur/polypyrrole/multi-walled carbon nanotube nanocomposite cathode with core–shell tubular structure for lithium rechargeable batteries

A multi-walled carbon nanotube and polypyrrole composite (PPy/MWNT) was synthesized by in situ polymerization of pyrrole monomer on the surface of MWNT. As-prepared PPy/MWNT composite was mixed with an aqueous suspension of nanosized sulfur particle, followed by heat-treatment to obtain an S/PPy/MWNT ternary composite. High resolution transmission electronic microscopy shows the formation of a highly developed core–shell tubular structure consisting of PPy/MWNT composite with uniform sulfur coating on its surface. Polypyrrole, with its high adhesion ability to MWNT, acts as a binder to connect sulfur and MWNTs, as well as absorbs polysulfides into its porous structure to improve the cyclability of the S/PPy/MWNT composite in Li/S batteries. The MWNT core provides a highly conductive and mechanically flexible framework, enhancing the electronic conductivity and consequently the rate capability of the material. This ternary composite cathode sustains 960.7 mAh g− 1 reversible specific discharge capacity after 40 cycles at 0.1 C, and 523.2 mAh g− 1 at 0.5 C.