Sulfur loaded in curved graphene and coated with conductive polyaniline: Preparation and performance as a cathode for lithium-sulfur batteries

We report a composite (CG-S@PANI), sulfur (S) loaded in curved graphene (CG) and coated with conductive polyaniline (PANI), as a cathode for lithium-sulfur batteries. CG is prepared by splitting multi-wall carbon nanotubes and loaded with S via chemical deposition and then coated with polyaniline via in situ polymerization under the control of ascorbic acid. The physical and electrochemical performances of the resulting CG-S@PANI are investigated by nitrogen adsorption-desorption isotherms, X-ray powder diffraction, thermogravimetric analysis, transmission electron microscopy, electrochemical impedance spectroscopy, charge-discharge tests, and electronic conductivity measurements. CG-S@PANI as a cathode for lithium-sulfur batteries delivers an initial discharge capacity of 851 mA h g^-1 (616 mA h g^-1 on the basis of the cathode mass) at 0.2 C with a capacity retention of over 90% after 100 cycles. This nature is attributed to the co-contribution of CG and conductive PANI to the concurrent improvement in electronic conductivity and chemical stability of the sulfur cathode.