Layered MoS2–graphene composites for supercapacitor applications with enhanced capacitive performance

Abstract

Layered molybdenum disulfide (MoS2)–graphene composite is synthesized by a modified l-cysteine-assisted solution-phase method. The structural characterization of the composites by energy dispersive X-ray analysis, X-ray powder diffraction, Fourier transform infrared spectroscopy, XPS, Raman, and transmission electron microscope indicates that layered MoS2–graphene coalescing into three-dimensional sphere-like architecture. The electrochemical performances of the composites are evaluated by cyclic voltammogram, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Electrochemical measurements reveal that the maximum specific capacitance of the MoS2–graphene electrodes reaches up to 243 F g−1 at a discharge current density 1 A g−1. The energy density is 73.5 Wh kg−1 at a power density of 19.8 kW kg−1. The MoS2–graphene composites electrode shows good long-term cyclic stability (only 7.7% decrease in specific capacitance after 1000 cycles at a current density of 1 A g−1). The enhancement in specific capacitance and cycling stability is believed to be due to the 3D MoS2–graphene interconnected conductive network which promotes not only efficient charge transport and facilitates the electrolyte diffusion, but also prevents effectively the volume expansion/contraction and aggregation of electroactive materials during charge–discharge process. Taken together, this work indicates MoS2–graphene composites are promising electrode material for high-performance supercapacitors.