Synthesis and Electrochemical Performance of Polypyrrole-Coated Sulfur/Multi-Walled Carbon Nanotube Composite Cathode Materials for Lithium/Sulfur Batteries

Abstract

In situ chemical oxidation polymerization of pyrrole on the surface of sulfur/multi-walled carbon nanotube particle was carried out to synthesize a novel polypyrrole coated sulfur/multi-walled carbon nanotube (PPy@S/MWCNT) composite. The sulfur/multi-walled carbon nanotube composite (S/MWCNT) was prepared by a facile quasi-emulsion template method in an oil/water system. The ternary PPy@S/MWCNT composite was characterized by elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. In the composite, polypyrrole works as a conducting matrix as well as a coating agent, confining the active materials within the electrode, while the MWCNT creates a highly conductive and mechanically flexible framework, hence enhancing the electronic conductivity and the rate capability of the material. This ternary composite exhibits stable cyclability, retaining a discharge capacity of 612 mAh g-1 at 0.1 C after 100 cycles. Furthermore, up to 1.5 C rate, the ternary composite still delivered a highly reversible discharge capacity of 463 mAh g-1.