Core@shell sulfur@polypyrrole nanoparticles sandwiched in graphene sheets as cathode for lithium-sulfur batteries

A nano sulfur-based composite cathode material featured by uniform core@shell-structured sulfur@polypyrrole nanoparticles sandwiched in three-dimensional graphene sheets conductive network (S@PPy/GS) is fabricated via a facile solution-based method. The S@PPy nanoparticles are synthesized by in situ chemical oxidative polymerization of pyrrole on the surface of sulfur particles, and then graphene sheets are covered outside the S@PPy nanoparticles, forming a three-dimensional conductive network. When evaluating the electrochemical performance of S@PPy/GS in a lithium-sulfur battery, it delivers large discharge capacity, excellent cycle stability, and good rate capability. The initial discharge capacity is up to 1040 mAh/g at 0.1 C, the capacity can remain 537.8 mAh/g at 0.2 C after 200 cycles, even at a higher rate of 1 C, the specific capacity still reaches 566.5 mAh/g. The good electrochemical performance is attributed to the unique structure of S@PPy/GS, which can not only provide an excellent transport of lithium and electron ions within the electrodes, but also retard the shuttle effect of soluble lithium polysulfides effectively, thus plays a positive role in building better lithium-sulfur batteries. (C) 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.