Study On Metal Oxide/Carbon-based Composites For Supercapacitors

In order to realize the sustainable development,the global energy crisis has become more and more important,and more efficient use of energy has become a hot research field now.Therefore,the research on the energy storage/conversion device of progressive electrode materials is also greatly stimulated.The character of the supercapacitor current is very satisfactory,such as high power density,faster charge or discharge rate,excellent cycle stability and wider operating temperature range.The main performance of supercapacitor is the activity and kinetic characteristics of electrode materials.The reasonable selection of electrode material and the advantage of the structure can effectively improve the activity and kinetic characteristics of the electrode material,thus improving the electrochemical performance of the supercapacitor.1?Multiwalled carbon nanotubes?MWNTs?and manganese dioxide?MnO₂?composites were prepared successfully by polyvinylpyrrolidone?PVP?assisted hydrothermal method and high temperature annealing.The morphology and structure of MnO₂/MWNT composites were characterized via TEM,XRD and XPS.The results show that well-dispersed MnO₂ nanoparticles adhered on the surface of MWNTs,and that the mass content of MnO₂ is 31.26%.The nanocomposite displays a high specific capacitance of 285.12 F/g at a current density of 1 A/g in 1 M Na2SO4 electrolyte.It exhibits good cycling stability and high capacitance retention,which is a good electrode material for supercapacitors.2?MnO₂/NG composites were synthesized using PSS as dispersing agent,GO,MnSO₄·H₂O,H₂O₂ and urea as starting materials.The morphology and structure of the composites were characterized in detail.The result shows that the well-dispersed MnO₂ nanoparticles with uniform size adhered on the surface of graphene,and nitrogen atoms are doped into the graphene lattice at the same time.Cyclic voltammetry and galvanostatic charging/discharging tests were carried out on capacitive properties of MnO₂/NG nanocomposites.Due to good capacitance performance of MnO₂ and good electronic transmission performance of the graphene-based material,the effective compounding in nanoscale leads to better charging and discharging properties.On the other hand,the testresults indicate: the electrode material has excellent cycle stability?only 11.1% of the capacitance reduced after 1000 cycles?at a current density of 1A/g and with the capacitance of the composite up to 302 F/g.In addition,MnO₂/NG is a promising supercapacitor electrode material with low cost,environmental friendliness and good capacitive performance.3?One step synthesis of tin oxide?SnO₂?and single walled carbon nanohorn?SWCNH?composite material was carried out by using SWCNHs and SnCl₄·H₂O as raw materials.The surface morphology,structure and composition of SnO₂/SWCNHs were characterized by TEM,XRD,AFM and XPS.And the electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge discharge tests.Due to the agglomeration of SWCNHs,its power and cycle stability should be low.The results show that the specific capacitance of the SnO₂/SWCNHs composites can be as high as 180.69F/g at current density of 1 A/g,SnO₂/SWCNHs has high capacitance retention,and when current density increased from 1 A/g to 10 A/g,the capacity retention rate is still up to86.5%,Since the SnO₂/SWCNHs has good cycle stability,the capacitance retention rate is up to 80.72% after 1200 cycles of charge and discharge.Therefore,the SnO₂/SWCNH nanocomposites are very suitable to be used as ideal electrode materials for supercapacitors.