Preparation And Modification Of MnO₂/C Composite Electrode Materials And Its Research On Capacitive Performance

With the development of green energy,supercapacitor,which has high power density,less demanding of work environment and superior cycle lifetime,attracts lots of researchers'attention.Based on the fundamental charge storage mechanism,supercapacitors can be classified into two types,i.e.electrical double-layer capacitors?EDLCs?based on carbon materials and pseudocapacitors based on transition metal oxides.EDLCs based on carbon materials has high charge-discharge rate and good cycle stability,but low energy density.While pseudocapacitors based on transition metal oxides has good reversibility and high energy density,but bad cycle stability.Therefore,it is significant to produce electrode materials with high energy and power density,good stability and low cost for the practical application of supercapacitor.This paper focuses on the capacitive performances of graphene?GR?,carbon nanotube?CNT?and manganese dioxide.Graphene and carbon nanotube were treated through microwave plasma technology,exploring the capacitive performance of graphene after plasma treatment and GR/CNT composites.What was more,the different manganese dioxide and carbon materials composites were synthesized through solvothermal method,following with the investigation of capacitive performance of manganese dioxides with different supporters.The main conclusions are as follows:?1?With plasma modification,graphene can maintain structure integrity to a certain extent,benefit for the play of the excellent capacitive performance of graphene,proved by the electrochemical test.When the two electrode capacitor is assembled using graphene oxide treated by the hydrogen plasma,the energy density of capacitor is 3.05 w.h/kg at the current density of 0.1 A/g.And the capacitance of capacitor retain 70%after 1000 cycles.?2?The structure and capacitive performance of the composites are different,when different carbon nanotubes and graphene make up into composites.Among different carbon nanotubes,the carbon nanotube treated by acid and graphene can form stable embedded structure,which exhibits better capacitive performance.When the capacitor is assembled using carbon nanotube treated by acid and graphene composite,the energy density is 3.90 w.h/kg at the current density of 0.1 A/g.And the capacitance of capacitor retain 96.6%after 800 cycles.?3?Through solvothermal method,manganese dioxide and carbon materials make up different composites.When it comes to manganese dioxide and carbon nanotube,MnO₂can load on the outer wall of CNT,which develops utilization of MnO₂ in electrolyte and conductivity of the material.While it comes to MnO₂ and graphene,the slice-like manganese dioxide is distributed on the surface of graphene.And the composite has overlapping graphene and large particles of manganese dioxide,the structure of which can not form complement,resulting in worse capacitive performance of composite.What is more,the structure of MnO₂/CNT/GR is designed,combined into the structure feature of MnO₂/CNT.When the capacitor is assembled using MnO₂/CNT/GR composite,the energy density is 4.74 w.h/kg at the current density of 0.1 A/g.And the capacitance of capacitor retain 83.72%after 1000 cycles.