Preparation And Capacitance Properties Of Core/Shell Nano Bimetallic Oxide

Supercapacitors,widely used energy storage devices have drawn great interests of researchers due to their fast charging/discharging rate,high power density,excellent cycling stabilities and superior lifetime.Electrode material which is an important part of the supercapacitor directly affects the energy storage of the capacitor.Therefore,the research of electrode material is still the forefront of the field of supercapacitor issues.It is not difficult to find that a single electrode material is hard to meet a wide range of requirements,so we focus on the study of composite materials,especially for the core/shell nanoparticles.In this paper,FeOOH@MnO₂,Fe₃O₄@MnO₂ and Fe₂O₃@MnO₂ nanomaterials with core/shell structure were successfully prepared in the presence of no template and surface additive at room temperature.The morphology,structure,composition and electrochemical properties of core/shell nanoparticles prepared by this method were studied.The thesis consists of three parts as following:Part Ⅰ:Preparation and capacitance properties of FeOOH/MnO₂ core/shell nanoparticlesAt room temperature,bimetallic oxide FeOOH@MnO₂ with unique core/shell structure was successfully prepared.The physical characterization of SEM and XRD,TEM and electrochemical properties were studied.It is proved that the core/shell structure of FeOOH@MnO₂ nanomaterials is uniformly dispersed and has a large specific surface area.As supercapacitor electrode materials,the core/shell FeOOH@MnO₂ nanomaterials not only have a large specific capacity but also have excellent cycle stability and coulomb efficiency.Part Ⅱ:Preparation and capacitance properties of Fe₃O₄/MnO₂ core/shell nanoparticlesThe bimetallic oxide Fe₃O₄@MnO₂ with unique core/shell structure was successfully prepared by two-step reaction without adding any surfactant.The core/shell structure was confirmed by SEM and XRD.Shell MnO₂ uniformly covered the surface of each spherical Fe₃O₄ nanoparticle,which made Fe₃O₄@MnO₂ similar to the shape of sea urchin.Fe₃O₄@MnO₂ nanoparticles had a large specific surface area by BET test.Electrochemical performance studies have shown that the core/shell structure Fe₃O₄@MnO₂ was optimistic about the electrochemical capacity and cycling stability of the supercapacitor electrode materials.Part Ⅲ:Preparation and capacitance properties of Fe₂O₃/MnO₂ core/shell nanoparticlesIn this chapter,Fe₂O₃@MnO₂ nanoparticles with core/shell structure were successfully prepared without adding any adjuvant at room temperature.The core/shell structure was confirmed by SEM and XRD.Electrochemical studies have found that the shell MnO₂ increased the specific surface area,ion transport efficiency and Fe₂O₃@MnO₂ specific capacity.Core Fe₂O₃ could significantly reduce the deformation of MnO₂ and improve the cycling stability of the composites.