Synthesis, characterization and cyclability of sulfur-polypyrrole composite as a cathode material for lithium secondary batteries

In this research، a sulfur-polypyrrole composite as cathode material of lithium-sulfur batteries was synthesized and evaluated. Polypyrrole conductive polymer was precipitated on the surface of sulfur particles by in-situ polymerization of pyrrole monomer with FeCl3 as the oxidizing agent. The synthesized composite was characterized by Fourier Transform Infrared Spectroscopy، X-ray diffraction، thermogravimetric analysis and scanning electron microscopy. The results of these experiments showed that polypyrrole was synthesized properly on the surface of sulfur particles and no chemical reaction occurred between them. Performance experiments showed that polypyrrole coating leads to increase the specific capacity and columbic efficiency and improve the cyclability of cathode material. A reversible capacity of 502 mAh g-1 was obtained for composite cathode after 50 cycles، which is ~4 times higher thansulfur cathode. The improved performance of the composite cathode is attributed to the enhanced electrical conductivity of cathode material and prevention of “shuttle phenomenon” with addition of polypyrrole.