Polyphenylene Wrapped Sulfur/Multi-Walled Carbon Nano-Tubes via Spontaneous Grafting of Diazonium Salt for Improved Electrochemical Performance of Lithium-Sulfur Battery

A novel conducting polymer polyphenylene is used to in situ wrap the MWCNT-core/Sulfur-shell composite via the spontaneous polymerization reaction process of benzenediazonium tetrafluoroborate (ArN2+ BF4−). The porous conductive polymer skin layer effectively prevents the dissolution of active sulfur and facilitates the diffusion of lithium ion towards to reaction site, due to the shortened diffusion distance. Moreover, this resulting architecture structure, Polyphenylene/S/MWCNTs, can accommodate the large volumetric expansion of sulfur during lithiation procedure, improving the cycling stability and rate capability of lithium-sulfur batteries. It delivers an initial discharge capacity of 1491.3 mAh/g at 0.1 C, and the remaining capacity is 1015.6 mAh/g after 75 cycles. The as-prepared material also exhibits an excellent rate capability and cyclability at 0.5 C, 1 C and 5 C. Our experimental results manifest that this composite is a potential candidate as cathode material for high performance lithium-sulfur batteries in the future.