A conductive polypyrrole-coated, sulfur-carbon nanotube composite for use in lithium-sulfur batteries
A novel ternary composite, polypyrrole (PPy)-coated sulphur-carbon nanotube (S-CNT), is synthesised by using an in situ, one-pot method. Firstly, elemental sulfur is loaded into the CNT network by a solution-based processing technique. Then conducting PPy is coated on the surface of the S-CNT composite to form the S-CNT-PPy ternary composite by carrying out polymerization of the pyrrole monomer in situ. The ternary composite is tested as a cathode for lithium-sulfur batteries. The results show that PPy coating improves significantly the performance of the binary composites (S-CNT and S-PPy). The conducting PPy is believed to serve multiple functions in the composite: as a conducting additive, an active material, and an adsorbent and container to confine the polysulfides and prevent them from dissolving into the electrolyte. As a result, PPy coating on the S-CNT composite enhances its conductivity, capacity and cycling stability. The capacity of S-CNT-PPy is about 600 mAh g-1 after 40 cycles, which is much higher than for the S-CNT composite (430 mAh g -1). 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.