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Sulfur/graphene composites with different sulfur contents were prepared by two-step synthesis, where graphene was regarded as a carrier of sulfur active substance. The surface structure and crystal form of the composites obtained were characterized and compared by X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). It was found that sulfur was partially coated by graphene. The graphene folds provided more nano-pores and electron transport channels for sulfur. From TGA results, the sulfur contents of the sulfur/graphene composites measured were about 42.32 wt%, 54.94 wt%, and 65.23 wt%. Electrochemical tests demonstrated that sulfur/graphene composite(x=54.94 wt%) cathode exhibited better capacity retention(40.13%) compared with the pure cathode(20.46%), where an initial discharge capacity was up to 1 500 m Ah·g-1 and it remained about 600 m Ah·g-1 after 30 cycles. Furthermore, the electrochemical reaction mechanism and the state of reaction interface for Li/S battery were analyzed by cyclic voltammogram and AC-impedance spectra. The results indicated that the sulfur/graphene composite with a sulfur content of 54.94 wt%, based on a two-step synthesis, contributed to improving electrochemical properties of lithium/sulfur battery
Sulfur / graphene composites with different sulfur contents were prepared by two-step synthesis, where graphene was deemed as a carrier of sulfur active substance. The surface structure and crystal form of the composites were obtained and compared by X-ray diffraction (XRD) , scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that sulfur was partially coated by graphene. The graphene folds provided more nano-pores and electron transport channels for sulfur. From TGA results, the sulfur contents of The sulfur / graphene composites were measured at about 42.32 wt%, 54.94 wt%, and 65.23 wt%. Electrochemical tests demonstrated that sulfur / graphene composite (x = 54.94 wt% (20.46%), where an initial discharge capacity was up to 1 500 m Ah · g-1 and it remained about 600 m Ah · g-1 after 30 cycles. Furthermore, the electrochemical reaction mechanism and the state of re action results for Li / S battery were analyzed by cyclic voltammogram and AC-impedance spectra. The results indicated that the sulfur / graphene composite with a sulfur content of 54.94 wt%, based on a two-step synthesis, contributed to improving electrochemical properties of lithium / sulfur battery