Synthesis And Electrochemical Performance Of Molybdenum Disulfide Composites

With the development of society and economy,the energy crisis has attracted widespread attention.Supercapacitor as the energy storage device with high power density,fast charge and discharge,long cycle life,become a research hotspot in the field of new energy.Molybdenum disulfide,as a kind of important two-dimensional laminar nano materials,with its unique "sandwich layer" layered structure has been widely applied in lubricants,catalysis,energy storage,composite materials and many other fields.Layers of MoS₂ are combined by weak van der Waals force,and electrons can transfer freely between layers,which makes MoS₂ becomes an ideal electrode materials.But molybdenum disulfide still exist some questions including easier reunite,smaller specific surface area,thicker and so on in the practical application.Apart from this,MoS₂ has the limited the abilities of cycle performance and energy storage due to its poor conductivity and volume change during the charge-discharge process.In view of the above problems,this thesis mainly carried out the following content:（1）Using ammonium molybdate as the source of molybdenum,thiourea as the source of sulfur synthesized different morphologies of MoS₂ nanomaterials including flower-like MoS₂,MoS₂ nanosheets,and spherical MoS₂ by hydrothermal method.The effects of reaction conditions on the morphologies and structures of MoS₂ such as the proportion of the sulfur atom and molybdenum atom,reaction temperature,reaction time,pH,kinds of surfactants were studied.In addition,the growth mechanism of MoS₂ was explored preliminarily and the electrochemical performances of MoS₂ with different morphologies were researched.The results show that the specific capacitances of flower-like MoS₂,MoS₂ nanosheets and spherical MoS₂ are 93.7 F/g,221.2 F/g and 60 F/g respectively at a current density of 1 A/g.（2）Using graphene oxide as a template,ammonium molybdate as the source of molybdenum,thiourea as the source of sulfur synthesized molybdenum disulfide/reduced graphene oxide composites through the hydrothermal method.The influence of the adding amount of thiourea on the structures of composites,and the influence of the dosage of graphene oxide on the morphologies and structures and the electrochemical performances of composites were studied.The research results show that MoS₂ in composites has the thinnest layers and stable structure when the content of thiourea is 4.0 g.Too much or too little thiourea can cause defects in molybdenum disulfide,which leads to the sample is not stable and easy to be oxidated by laser.MoS₂ in composites has the thinnest layers and can disperse uniformly in gossamer graphene,when the dosage of graphene oxide is 800 mg.The structure of this composite not only can make it contact with the electrolyte solution fully but also can improve the electrical conductivity of material,which makes it better applied to the supercapacitor electrode.Electrochemical performance tests show that the specific capacitance of this electrode material is 310 F/g,and keeps about 230 F/g after 500 cycles at a current density of 1 A/g.（3）Synthesized（molybdenum disulfide/reduced graphene oxide）@ polyaniline ternary composites through in situ polymerization method.The influences of the content of polyaniline on the morphologies and structures and the electrochemical performances of composites were studied.Research results show that polyaniline composites appeared smaller and more pore with the increase of the content of polyaniline,which is advantageous to the transportation of the ions inside the material.The ternary composite that the content of polyaniline is 80% possesses higher specific capacitance and better cycle stability compared with MoS₂/rGO composites and the ternary composites with other contents of polyaniline.The specific capacitance of this electrode material is 570 F/g,and keeps about 445 F/g after 500 cycles at a current density of 1 A/g.