The Preparation Of Flexible RGO/CNT/MnO₂ Composite Electrode Materials And The Research Of Their Capacitance Performances

In view of the global energy shortages and environmental degradation, all kinds of recycled green electrochemical energy storage devices brought lots of attention. Supercapacitor which is known as a new energy storage device, has many advantages such as large power density, long cycle life and pollution-free, thus attracted much attention and research. And as the rapid development of portable wearable electronic digital products, energy storage that has certain flexibility performance becomes a research hotspot in recent years. The choice of the electrode materials is the key factor to the performances of flexible supercapacitor. Metal oxides and carbon materials are widely used as electrode materials, the combining of metal oxides and carbon materials to preparing composite electrode materials with good electrochemical and flexibility performances, becomes a new subject for research scholars.This paper revolves around the preparation and characterization of reduction graphene oxide（RGO） and the preparation and characterization of RGO/Mn O₂ and CNT/Mn O₂ composite materials, as well as the preparation and performance characterization of flexible composite electrode which is based on the collector made by CNT/CF. Eventually using conductive carbon fiber and CNT as raw materials to prepare the flexible collector, and the fresh prepared RGO/Mn O₂, CNT/Mn O₂ composites were loaded to the collector by sucking filtration to form flexible composite electrode materials. Cyclic voltammetry, AC impedance method, and constant current charge and discharge test were carried on the as-preparated electrode materials to measure their electrochemical performances.Microwave hydrothermal method was used to prepare RGO. Graphene Oxide（GO） as raw material, glucose, urea, vitamin C, L-cysteine was used as reducing agents, respectively. Physical and chemical properties test were carried on various kinds of as-prepared RGO, especially the dispersion in many aqueous solutions. Through the test results we choice glucose as the best reductant. Then we optimized the reduction condition, to find out the best process for the preparation of RGO. They are glucose as the reducing agent, alkaline condition（p H=9）, microwave hydrothermal reducing at 95 °C and holding 120 min. Then, the as-prepared RGO powder used as active material, electrochemical tests showed it has good capacitance characteristics.As a comparison, ultrasonic coprecipitation was used to prepare RGO/Mn O₂ and CNT/Mn O₂ composites, potassium permanganate and manganese sulfate were chosen as the source of manganese, while CNT and RGO as based materials, by changing the concentration of manganese ion, to prepared different samples. RGO/Mn O₂, CNT/Mn O₂ composites with multistage micro/nano structure also have been prepared. Those as-prepared composite materials used as active substance to prepare RGO/Mn O₂ or CNT/Mn O₂ electrodes, respectively. The specific capacitance of RGO/Mn O₂ electrode is about 180 F/g at a scanning rate of 2 m V/s. The specific capacitance of CNT/Mn O₂ electrode is about 480 F/g at the same scanning rate.Microwave hydrothermal method was used to prepare RGO/Mn O₂ and CNT/Mn O₂ composite, potassium permanganate was chosen as the source of manganese, while CNT and RGO as raw material, by changing the concentration of manganese ion, to prepared different samples. RGO/Mn O₂, CNT/Mn O₂ composites with multistage micro/nano structure have been prepared. Those as-prepared composite materials used as active substance to prepare RGO/Mn O₂ or CNT/Mn O₂ electrodes, respectively. The specific capacitance of CNT/Mn O₂ electrode is about 364 F/g.Carbon nanotubes and carbon fibers are used as raw materials to prepare flexible collector（CC）. The collector has good electrical conductivity and porous network structure, the material has certain mechanical strength and also has the good flexibility. Fresh prepared RGO/Mn O₂ composites were loaded to the collector surface by sucking filtration, and a flexible composite electrode was obtained（which named as CCRM）.The electrode material has good electrochemical performances and stable performance. The specific capacitance of CCRM electrode is about 360 F/g at the scanning rate of 2 m V/s. Similarly, the fresh prepared CNT/Mn O₂ composites suction filter to the as-prepared collector surface, and the flexible composite electrode material（named as CCCM） was obtained. The electrode material has good electrochemical performance and stable performance. The capacitance of RGO/Mn O₂ electrode is about 366 F/g. Finally, fresh prepared CNT/Mn O₂ composites with a certain volume of RGO dispersion mixed together, to form a homogeneous mixture, then the mixture suction filter to the as-prepared collector surface, to prepare flexible composite electrode materials（named as CCCMR）, the electrode material has good electrochemical performance and stable performance, the specific capacitance of the electrode is about 390 F/g at a scanning rate of 2 m V/s.