Preparation And Performance In Supercapacitors Of MoS₂@Carbon Composite Electrode Materials

Supercapacitors are new energy storage devices,complementary to traditional capacitors and secondary batteries,which have been used in energy recovery,improve vehicle power performance and battery protection and other automotive field.They have the advantages of high power density,fast charging/discharging rates and long cycle life.The performance of supercapacitors greatly depend on their electrode materials.At present,electrode materials for supercapacitors are carbonaceous materials,transition-metal oxides and conducting polymers.MoS₂ has a special layered structure and a high theoretical specific capacity,which attracts widespread attention.However,its poor conductivity resulting in poor electrochemical properties.MoS₂ nanosheets were prepared by direct ultrasonic exfoliation method by adding sodium cholate.The results of SEM and TEM showed that the MoS₂ nanosheets with uniform size have been layered well,and the specific surface area measured by nitrogen adsorption desorption test is 8310.947 m2 / g.The results also showed that the concentration of sodium cholate have a significant effect on the stripping of MoS₂ nanosheets,i.e.the average scale of MoS₂ nanosheets decreased with the increase of sodium cholate concentration,and the yield also drops.In addition,with the increase of the concentration of bulk MoS₂,the average scale of MoS₂ nanosheets increases,while the uniformity of the scale is deteriorated and the exfoliation effect is also deteriorated.The absorbance of MoS₂ nanosheets dispersions was measured by UV spectrophotometry.The results showed that the absorbance of MoS₂ nanosheets dispersions decreased with the increase of sodium cholate concentration,and increased significantly with the increase of ultrasonic time.MoS₂ nanosheets@C composites with core-shell structure were prepared by micelle anchored method.MoS₂ nanosheets were incorporated on the surface of activated carbon with good conductivity by method of micellar anchoring and hydrothermal synthesis.MoS₂ nanosheets@C composite electrode material with good electrochemical performance has thus been prepared for supercapacitors.During the synthesis,hexadecyl trimethyl ammonium bromide?CTAB?micelles assembled to solubilize activated carbon and anchor MoS₂ nanosheets onto the carbon surface.Structure and Morphology characterization showed that monodisperse MoS₂ nanosheets tiled on the surface of the activated carbon,formating the strcture of activated carbon as the core and the MoS₂ nanosheets as the shell.Due to the increased electric conductivity and high specific surface area,the electrochemical performance showed that MoS₂ nanosheets@C composites exhibited a specific capacitance of 163.5 F/g at 0.1 A/g,which surpasses those of their individual counterparts?127 F/g and 13.7 F/g at 0.1 A/g for activated carbon and MoS₂ nanosheets,respectively?.The composites also showed good cycling stability due to structure support of the inner carbon cores?capacity retention of 90% after 1000 cycles?.Results show that the MoS₂ nanosheets@C composites are promising electrode materials for supercapacitors.