Research On Hybrid Supercapacitors With Nanomaterials Of Manganese Dioxide And Zinc Oxide

Hybrid supercapacitor is a device beared the advantages of secondary battery as well as supercapacitor,which has high energy density,high power density and long cycle life.Therefore this device will have a good application prospect.This thesis first reviewed the research progress of the current study of the hybrid supercapacitor,and then present our research ideas through the synthesis and characterization of the electrode materials,and investigated their electrochemical performance in a hybrid supercapacitor.The main research contents and results are list as follows:The composite material which comprises manganese dioxide and activated carbon was synthesised by impregnation method.The manganese dioxide was affirmed as an amorphous brinessite-type?-MnO₂ and highly dispersed within the microporous structure of activated carbon materials.The composite material comprised manganese dioxide and activated carbon was used as anode,nitrogen highly ordered mesoporous carbon materials was used as cathode,and the Hydrogen ion hybrid supercapacitor assembled by the anode and the cathode was tested in 1 M Sodium sulfate solution.The active material of anode contains nitrogen functional groups,which has the capability of making hydrogen evolution overpotential more negative,And,manganese dioxide has the capability of making oxygen evolution overpotential more positive.So it greatly improves the hybrid supercapacitor's working voltage window reached about 2.1 V in the aqueous solution.In addition,energy density of hybrid supercapacitor is improved by increasing the working voltage window,according to the energy density equlation E=1/2CU².The energy density can reach 40.8 mAh g^-1 under 100 mA g^-1 current density of discharge.The hybrid supercapacitor has a good cycling stability,which was demonstrated for 150cycles in a current rate of 100 mA g^-1.Flower-like zinc oxide was synthesised by hydrothermal method,and nano-crystal zinc oxide was obtained by calcinated flower-like zinc oxide at 800?.The composite material,polydopamine coated nano-crystal Zinc oxide,was synthesised through the self-polymerization of dopamine and coated on the surface of nano-crystal zinc oxide.This the composite material was then carbonized to get the carbon coated nano-crystal zinc oxide material.All the materials synthesised were characterized by SEM,TEM,XRD XPS and Raman spectrascopy.The size of nano-crystal zinc oxide was found to be 50-200 nm and the crystal structure is the wurtzite phase of hexagonal zinc oxide.Furtheremore,it was found that nano-crystal zinc oxide not only successfully loaded into conductive carbon materials,but also kept its morphology and structure after the coating.In addition,nano-crystal zinc oxide and carbon coated nano-crystal zinc oxide were used as the anode materials assembled with activated carbon to obtain lithium ion hybrid supercapacitor,respectively.The electrochemical test was carried out in 1 M LiPF₆ with 1:1 ethyl carbonate?EC?:dimethyl carbonate?DMC?.The electrochemical investigation results showed that the carbon coated nano-crystal zinc oxide has higher coulomb efficiency,rate performance and cycle performance than those of nano-crystal zinc oxide.The energy density of lithium ion hybrid supercapacitors assembled by carbon coated nano-crystal zinc oxide and active carbon?ZnO/C//AC?is four times compared with lithium ion hybrid supercapacitors assembled by nano-crystal zinc oxide and active carbon?ZnO//AC?at the current density of 100 mA g^-1...