S-doped graphene/mixed-valent manganese oxides composite electrode with superior performance for supercapacitors

Abstract

Sulfur doping is one of the most promising approaches to generate electron-dense active region on the surface of graphene-based materials. This work developed an environmental friendly method for synthesizing sulfur-doped graphene (SG)/mixed-valent manganese oxides (MnOx). Three-dimensional (3D) SG is prepared by thermal treatment, and the uniformly doped sulfur provided more anchor points for the compound of subsequent mixed-valent manganese oxides. The final product SG-MnOx (x stands for mixed valence) composite was obtained by one-pot hydrothermal method in which mixed-valence manganese oxides were synthetized and compounded the SG simultaneously. The specific capacitance of SG-MnOx electrode at 0.5 A g−1 is 1311 F g−1 and the long-life cycle retention after 5000 cycles is 81.2%. The excellent manifestation of supercapacitors primarily attributed to the sulfur doping and synergistic effect with MnOx compound. This allows the SG-MnOx electrode to exhibit much better electrochemical performance than the two individual materials. The asymmetric supercapacitor with SG-MnOx and AC exhibits an excellent energy density (21.23 Wh kg−1) with power density of 1.5 kW kg−1. The above performance indicates that SG-MnOx is one of the materials for supercapacitors with great promise.