Research On The Synthesis And Supercapacitor Performace Of Carbon Spheres/Mno₂by Hydrothermal

Supercapacitors, also called electrochemical supercapacitor, have been recognizedas new electrochemical energy devices which performance between the rechargeablebatteries and the dielectric capacitors. Supercapacitors mainly consist of the electrodeactive material of electrode, electrolyte, collector, diaphragm, lead and package material.At present, studies on supercapacitors are mainly focused on the preparation of highperformace electrode material. Supercapacitors electrode material can be divided intothree categories: carbon material, metal oxide and conductive polymer. With thedevelopment of society, the supercapacitors as energy saving, environmental protection,clean energy have attracted more and more attention, because of its high power density,huge discharging current instantly, long service life, low temperature performance, longtime, high reliability, high energy density, are widely used in the fields such as electricvehicles, information technology, consumer electronics, military force. Therefore, thesupercapacitors have very good development prospect.This paper selected new carbonaceous material, cheap manganese dioxide aselectrode material for supercapacitor, by integrating various electrochemical andmaterials methods, this dissertation has investigated thematerial preparation, electrodepreparation, capacitve properties, mechacism of supercapacitor and application. Weabstract the main content of this dissertation as following:1) systematic study on hydrothermal preparation method of carbon sphere,discusses the different preparation conditions on the formation of carbon sphere impact,such as reaction time, temperature, reactant concentration of carbon spheres andcombinations SEM, TEM diagram and relevant literature analysis the growthmechanism of carbon sphere. Tthe products consist of uniform sphericalnanometer-sized particles that have a diameter in the40–380nm range, which can bemodulated by modifying the synthesis conditions （i.e., the concentration between0.025mol/L⁰.1mol/L of the aqueous glucose solution, the reaction time between6h²4h, and the reaction temperature between180℃-240℃）. By exploring theelectrode prepation process, supercapacitor properties are studied by cylic voltammetryand constant-current charge-recharge. The experimental results show that, loringelectrode material through regulating the reaction conditions, nanometer carbon spherescan be synthesis, and the smaller the partical size is, the more prone to fusion①By expto generate a peanut shape or chain-shaped carbon sphere;②The smaller particlesize of the carbon sphere, the higher specific surface area is. The higher surface area ofthe hydrothermal carbon spheres as electrode material for supercapacitor, showingbetter electric double layer capacitor electrode behavior and better reverdibility.2) Through the hydrothermal method, we synthesize MnO₂powder electrodematerial of different crystalline and diferent morphologies. And we studied the effectsof different reactant concentrations, the different crystal type of MnO₂electrodematerial and the cycle life influence on the formation of crystal type for capacitorcharacteristics. We found that, in the potassium and sodium thiosulfate concentrationratio of1:1, the MnO₂powder crystal type is α type, when the concentration ratio of1:2,the prepared MnO2powder crystal type is γ type. The results showed that, γ-MnO2（194F/g） capacitance characteristics was better than the α-MnO₂（156F/g）.3) KMnO4and Na₂S₂O₃·5H₂O as raw materials, we synthesized MnO2@Ccore-shell composite material by a hydrothermal method, and analysis on its growthmechanism and electrochemical properties, combined of SEM, TEM diagram andrelevant literature. We found that, through the hydrothermal method, we couldsynthesize MnO₂@C core-shell composite material, and the average capacity was180.2F/g.