Polypyrrole-modified carbon nanotubes@manganese dioxide@sulfur composite for lithium–sulfur batteries

Lithium–sulfur (Li–S) battery is one of the most promising next-generation energy storage devices due to its high-capacity density and low cost. However, lithium–sulfur batteries could not be widely used in a large range due to the “shuttle effect” and sulfur insulation. Herein, we proposed a novel composite cathode of carbon nanotubes@manganese dioxide@sulfur@polypyrrole (C@MnO 2 @S@PPy). X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) BET analysis show that sulfur filled into the pores of C@MnO 2 , and PPy was successfully coated on C@MnO 2 @S. TG indicated that the compound contained 60 wt% active sulfur. The prepared cathode of C@MnO 2 @S@PPy composites shows excellent rate performance and cycle stability. At a high rate of 1C, its maximum discharge capacity reached 1218 mA h g-1 and its average capacity decreasing rate was only 0.096%/cycle when running over 500 cycles. The interaction mechanism of MnO 2 with polysulfides was investigated by adsorption tests and XPS analysis. The excellent electrochemical performance might be due to a combination of adsorption or catalytic properties of MnO 2 and the conductivity of carbon materials and PPy.