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° disappeared, while the relatively weak diffraction peak at 27° 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.