Study On The Capacitive Performance Of Molybdenum Disulfide/Three-dimensional Graphene Composite For Supercapacitor

Due to the growing problems of global energy shortage and environmental pollution,extensive researches works have been done by researchers in the field of energy conversion and energy storage.Supercapacitor as a new type of energy storage devices,because of its high power density,long cycle life and low maintenance cost,has great application potential in the field of energy storage,and has attracted widespread attention.The way of storing energy of supercapacitor mainly relies on the polarization of the electrolyte,in which the electrolyte ions may concentrate on opposite sides of the electrode.And according to the energy storage mechanism,the supercapacitor can be divided into electric double layer capacitor and pseudocapacitor.The electrode material of supercapacitor should be well-conductive and the microstructure of the electrode material is one vital factor influencing the capacitive performance,which means that increasing the active specific surface area is beneficial for the capacitive performance.According to the structure of electrode material,the electrode material can be divided into zero-dimensional material,one-dimensional material,two-dimensional material,and three-dimensional material.On the purpose of improving the capacitive performance,the suitable microstructure for the electrode material can be utilized to make the utmost of the active specific surface area based on the material performances.Monolayered/few-layered molybdenum disulfide（MoS₂）owns graphenelike two-dimensional structure,and the hierarchical MoS₂ nanosheets restacked by monolayered/few-layered MoS₂ nanosheets may permit the occurrence of the intercalation-deintercalation of electrolyte ions and energy can be stored by this way.In this paper,monolayered/few-layered MoS₂ nanosheets was prepared by liquid-exfoliation method,three-dimensional foam-like graphene（3DGN）was prepared by chemical vapor deposition（CVD）method,hierarchical MoS₂ nanosheets and 3DGN（MoS₂@3DGN）composite was prepared by the simple dipping-drying method.The scanning electron microscope（SEM）,transmission electron microscopy（TEM）,Raman spectroscopy,X-ray diffraction analysis（XRD）,X-ray photoelectron spectroscopy（XPS）,N2 adsorption-desorption method and ultraviolet absorption spectrum（UV-Vis）were employed the analyze the structure and composition,and electrochemical workstation was adopted to analyze the electrochemical performances.The structure testing results show that the hierarchical MoS₂ nanosheets own expanded interlayer spacing and are uncontinuously distributed on the surface of 3DGN.The hierarchical structure of MoS₂ nanosheets can make fully use of the intercalation-deintercalation mechanism and ensure the utmost utilization of the active specific surface area of MoS₂.And the introduction of 3DGN can improve the conductivity of the electrode and make more contact area between the electrode material and electrolyte.The electrochemical testing results show the remarkable electrochemical performance of MoS₂@3DGN.The composite can achieve 110.57% capacitance retention after 4000 cycles of galvanostatic charge/discharge tests and 76.73% capacitance retention with increasing the current density from 1 A ^g-1 to 100 A ^g-1.Moreover,the asymmetric coin cell supercapacitor using MoS₂@3DGN and active carbon as electrode materials is assembled.This device could achieve a working voltage window of 1.6 V along with the power and energy densities of 400.0-8001.6 W k^g-1 and 36.43-1.12 Wh k^g-1 respectively.Additionally,two coin cell supercapacitors in series were charged to 2.2 V and could power one LED indicator（starting voltage of 1.8-2.2 V,20 m A）for about four minutes.The remarkable performances indicate the favorable application potential of MoS₂@3DGN for supercapacitor electrodes.