Preparation of hierarchical porous carbon/sulfur composite based on lotus-leaves and its property for Li-S batteries

The carbon skeleton with high specific surface (572.1 m²/g) and large number of hierarchical pores especially micro-pores (average pore size at 3.2 nm) was obtained from common lotus-leaves by using multistage carbonization method. Ball milling and melting method were used to synthesize different S contents (48wt%/ 62wt%/71wt%) carbon/sulfur composite materials. XRD, FESEM, EDS, and TG were employed to analyze structure and morphology of the samples. The result indicated that element sulfur was uniformly accommodated in the skeletons which were composed by graphene-like layered structure and micrometer sticks. Charge/discharge tests at current density of 0.1C in the voltage range of 1.2-2.8 V showed that the initial discharge specific capacity of the carbon/sulfur composite (62wt%) reached 1246 mAh/g, and its capacity still remained 600 mAh/g even after 100 charge/discharge cycles. The results prove that the obtain composites can suppress the "shuttle effect" of polysulfide species effectively.