Investigation on fabrication of reduced graphene oxide-sulfur composite cathodes for Li-S battery via hydrothermal and thermal reduction methods

Abstract

Lithium-sulfur (Li-S) battery is considered one of the possible alternatives for next-gener-ation high energy batteries. However, its practical applications are still facing great challenges be-cause of poor electronic conductivity, large volume change, and polysulfides dissolution inducing “shuttle reaction” for the S cathode. Many strategies have been explored to alleviate the aforemen-tioned concerns. The most common approach is to embed S into carbonaceous matrix for construct-ing C-S composite cathodes. Herein, we fabricate the C-S cathode reduced graphene oxide-S (rGO-S) composites via one step hydrothermal and in-situ thermal reduction methods. The structural fea-tures and electrochemical properties in Li-S cells of the two type rGO-S composites are studied sys-tematically. The rGO-S composites prepared by one step hydrothermal method (rGO-S-HT) show relatively better comprehensive performance as compared with the ones by in-situ thermal reduction method (rGO-S-T). For instance, with a current density of 100 mA g−1, the rGO-S-HT composite cathodes possess an initial capacity of 1290 mAh g−1 and simultaneously exhibit stable cycling ca-pability. In particular, as increasing the current density to 1.0 A g−1, the rGO-S-HT cathode retains a reversible capacity of 582 mAh g−1 even after 200 cycles. The enhanced electrochemical properties can be attributed to small S particles uniformly distributed on rGO sheets enabling to significantly improve the conductivity of S and effectively buffer large volume change during lithiation/delithi-ation.