Study On The Preparation Of GR/CNTs/MnO₂ Hollow Composite Microspheres And Its Application In Supercapacitors

The supercapacitor has long been the greatest concern of the energy storage unit owing to its high power density,long cycling life,desirable safety and other characteristics,however its application has been limited because of its low energy density.One of the main factors that affect the performance of supercapacitors is electrode material,carbon materials,such as graphene?GR?and carbon nanotubes?CNTs?have become the focus of the research of electrode materials due to their good conductivity and large specific surface area.But these materials are easy to stack,agglomeration in the preparation process of GR,CNTs and other electrode materials.At the same time,its specific capacity is not large enough,those reasons hinder its application in supercapacitors.Transition metal manganese dioxide?MnO₂?has become one of the most potential metal oxide electrode materials because of its advantages such as simple preparation process,abundant resources,friendly environment and high theoretical capacity,however,there are some problems such as weak conductivity and poor cycle stability.Therefore,how to give full play to the advantages of a variety of electrode materials,and then the preparation of high-performance supercapacitor has become the focus of study.In order to overcome the problems of GR such as stacking and aggregation,and increase the specific surface area as well,the reduced graphene?RGO?hollow microspheres and GR hollow microspheres were prepared by polystyrene?PS?template method and silica?SiO₂?template method,respectively,and we first proposed to combine the hollow microspheres with CNTs and MnO92,by using synergistic effect between the components,the hollow composite electrode material with high specific capacitance and high conductivity was prepared.The main research work is as follows:PS microspheres were prepared by emulsion polymerization.and we use them as a template to prepare PS/GO composite microspheres by solution mixing method.The optimum condition for the coating of PS:GO with the mass ratio of 10:1 and the reaction temperature of 80 ? were given.Then RGO hollow microspheres were prepared by reduction of hydrazine hydrate.The SiO₂ microspheres were prepared by Stober methods,and the GR hollow microspheres were obtained by using the two phenol formaldehyde as the coating material and the carbonization of CVD at the temperature of 600 ? and the graphitization treatment at the temperature of 800 ?.CNTs were composited on the RGO and GR hollow microspheres by using solution mixing method and CVD method,respectively.Through the water bath method,RGO/CNTs/MnO₂ and GR/CNTs/MnO₂ three hollow composite materials were prepared.In the 1 mol/L Na2SO4 electrolyte,the specific capacitance of the composite electrode can reach 647.79 F/g at the sweep rate of 5 mV/s,which shows good electrochemical performance.