Supercapacitive Performances Of Hollow Nanostructural Materials

Supercapacitors（SCs）,as an important next generation energy storage device,have recently been attracting extensive interests due to their excellent combination of high energy and power density.Previous studies have shown that electrode material is one of dominating factors that influence the capacitive performance of SCs.Among various carbon electrode materials,hollow carbon spheres have attracted much interest due to their large void space fraction,porous shell,controllable surface properties and outstanding structural stability.So,hollow carbon spheres are considered as the most promising materials for practical SCs.In this thesis,the supercapacitive performance of these hollow carbon spheres is further improved by introducing the N-containing functional groups and metal oxide.In this thesis,we reported the preparation and supercapacitive performance of a series of hollow nanostructured materials,containing heteroatoms-doped double shell hollow carbon spheres（DHCS）,glucose-based hollow carbon spheres（HCS）and glucose-based hollow carbon sphere/MnO₂（HCS/MnO₂）.This thesis mainly contains the following contents:Glucose-based hollow carbon spheres are prepared by hard templating method.And glucose-based hollow carbon sphere/MnO₂（HCS/MnO₂）with different thickness of MnO₂ shells are then prepared by introducing MnO₂ on the shell of HCS using “in-situ grouth method”.The specific surface of HCS/MnO₂ decrease from 129.3 m2/g to 42.4 m2/g with the increase of the thickness of MnO₂ shell.Electrochemical data shows that the specific capacitance of the HCS/MnO₂ is greater than pristine carbon spheres in 6 mol/L KOH electrolyte.The specific capacitance of HCS/MnO₂ can reach 158.6 F/g at the current density of 1 A/g in 6 mol/L KOH electroyte.Whereas,the specific capacitance of HCS/MnO₂ can only reach to 72.0 F/g at the current density of 1 A/g in 1 mol/L Na2SO4 electroyte due to the low specific surface of HCS/MnO₂.A special “in-situ replicating” strategy is employed to fabricate double shell hollow carbon spheres with homogeneously doped heteroatoms using dopamine as carbon source.The KOH activation introduces micropores to the thin shells of the hollow carbon spheres.Materials characterizations show that these carbon spheres have such merits as large surface area,easy-accessible micropore surface with faradiac reaction sites,and high conductivity.All these result in ultrafast ion transport from electrolyte to the micropores in the carbon spheres and endow the carbon with outstanding capacitive performance,e.g.an unprecedentedly high specific capacitance of 270 F/g at a very high current density of 90 A/g.Moreover,a high energy density of 11.9 Wh/kg at a respectable power density of 30000 W/kg is achieved in 6 mol/L KOH electrolyte.