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Study On The Electrochemical Performances Of Hybrid Supercapacitor In MnO2//AC And LiMn2O4//AC System

Posted on:2013-07-16Degree:MasterType:Thesis
Country:ChinaCandidate:C YangFull Text:PDF
GTID:2252330392470400Subject:Materials science
Abstract/Summary:PDF Full Text Request
Hybrid supercapacitor (HESC) combines the advantages of high energy densityof batteries and high power density of the supercapacitors and has broad applicationprospects. In this thesis, the electrochemical performances of hybrid supercapacitor inMnO2//activated carbon (AC) and LiMn2O4//AC system were studied.MnO2was synthesized by KMnO4and MnSO4as raw materials and FeSO4asmodification. The structure and morphology of Fe-MnO2was characterized by XRDand SEM.The results showed that the Fe-MnO2pocessed the better electrochemicalproperties when the bath temperature was30C and the dopant of Fe was2wt.%. Itsspecific capacitance was210F/g at the current density of0.2A/g, improved up to12.7%when compared to that of pure MnO2. After assemble into the hybridsupercapacitor with activated carbon, the potential window with0-1.8V was high,and the maximum specific capacitance was43F/g at the current density of0.2A/g. Itshowed an energy density of19.4Wh/kg at a power density of180W/kg. When thepower density increased to1800W/kg, the energy density is still14Wh/kg.The LiMn2O4//AC hybrid supercapacitor consisted of a LiMn2O4positiveelectrode and AC negative electrode was assembled in1mol/L Li2SO4. The effect ofspecific surface area of the activated carbon, the mass ratio of anode and cathode,operating voltage range on the electrochemical performance of LiMn2O4//AC wereinvestigated. The result showed that the optimal experimental conditions wereoperating voltage range at01.8V, the surface area of the activated carbon with2000m2/g, the mass ratio of anode to cathode at1:2. Carbon nanotubes were introducedinto the positive electrode to make effective elctric-contact between LiMn2O4particlesand improve the LiMn2O4activity and utilization. The maximum specificcapacitanceof LiMn2O4//AC was85.9F/g with addition of1%CNT into positiveelectrode. It showed an energy density of38.26Wh/kg at a power density of2640.72W/kg. With the increase of the content of CNT, the specific capacitance of hybridsupercapacitor decreased, however, the power density improved compared withLiMn2O4//AC.
Keywords/Search Tags:Hybrid supercapacitor, Manganese oxide, Lithium manganese oxide, Activated carbon
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