Layered MoS_2-graphene composites for supercapacitor applications with enhanced capacitive performance

摘要

Layered molybdenum disulfide (MoS_2)-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 MoS_2-graphene coalescing into three-dimensional sphere-like architecture. The electrochemical performances of the composites are evaluated by cyclic voltammo-gram, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Electrochemical measurements reveal that the maximum specific capacitance of the MoS_2 -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 MoS_2-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 MoS_2-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 MoS_2-graphene composites are promising electrode material for high-performance supercapacitors.