Reduced graphene oxide encapsulated sulfur spheres for the lithium-sulfur battery cathode

Reduced graphene oxide (rGO) encapsulated sulfur spheres for the Li-S batteries were prepared via the redox reaction between sodium polysulfide. XRD spectra showed that the diffraction peak of graphite oxide (GO) at 10 degrees disappeared, while the relatively weak diffraction peak at 27 degrees belongs to graphene emerged. FT-IR spectra showed that the vibrations of the functional groups of GO, such as 3603 cm(-1), 1723 cm(-1) and 1619 cm(-1) which contributed from -OH, C-O-C and C=O respectively, disappeared when compared to the spectra of GSC. SEM observations indicated that the optimum experimental condition followed as: mass ratio of GO and S was 1: 1, 10% NaOH was used to adjust the pH. EDX analysis showed that the sulfur content reached at 68.8% of the composite material. The resultant electric resistance was nearly less than GO's resistance in three orders of magnitude under same condition. Further electrochemical performance tests showed a coulombic efficiency was 96% from the first cycle capacity was 827 mAh g(-1), to 388 mAh g(-1) in the 100 cycles. This study carries substantial significance to the development of Li-S battery cathode materials. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.