Study On Preparation And Electrochemical Properties Of Manganese Dioxide Based Electrode Materials For Supercapacitors

Low-cost MnO2 with various structures is a popular and environmentally-friendly supercapacitor material.However,due to the poor conductivity,compounding conductive materials are required to achieve its energy storage potential.In this work,MnO2 was compounded with pre-reduced graphene and N-doped graphene,respectively,and the corresponding electrochemical properties of the composites were studied.In this thesis,GO was trated with glucose to obtain the modified GO.HRGO/MnO2composites were prepared by the hydrothermal reaction of modified GO,KMnO4 and MnSO4.The characterization results demonstrate that the spherical MnO2 corresponds to?-MnO2,which is uniformly and stably combined with HRGO.BET test shows that the average pore diameter and the specific surface area of HRGO/MnO2 are 3.949 nm and159.1 m~2/g,respectively.Electrochemical performance test results exhibit that HRGO/MnO2 delivers the specific capacitance of 270 F/g at 0.5 A/g,the specific capacitance of 168 F/g can be retained when the current rises to 15 A/g,showing a capacitance retention rate of 62%,indicating excellent rate performance.The asymmetric supercapacitor assembled by HRGO/MnO2 and graphene gel delivers the specific capacitance of 76 F/g at the current density of 0.5 A/g.The supercapacitor can retain90.4%of the initial capacitance after 15000 cycles at 5 A/g,and the energy density reaches 30.10 Wh/kg at the power density of 945 W/kg.The composite of porous HNG/MnO2 was synthesized using urea as nitrogen source.The specific capacity of HNG/MnO2 can reach 246 F/g at 0.5 A/g,and the specific capacitance of 172 F/g remains at 10 A/g with the specific capacitance retention rate of70%.The asymmetric supercapacitor assembled by using HNG/MnO2 as the cathode and graphene hydrogel as the anode can contribute a specific capacitance of 71 F/g at 0.5 A/g,and the specific capacitance of 43 F/g can be obtained when the current density rises to 5A/g with the retention rate of 62%.In addition,the asymmetric supercapacitor can keep90.8%of its initial capacity after 3000 charge/discharge cycles at 5 A/g.