Preparation And Supercapacitor Performance Of Iron Oxide And Its Nanocomposites

As a new type of energy storage device,supercapacitor is used in electric vehicles,communication equipment and aerospace field.However,it presents low energy density,so the development of electrode materials for high-performance supercapacitor become one of the current focus.Iron oxide has the advantages of cheap,environmentally friendly and high theoretical capacitance and widely used as supercapacitor anode materials.In this thesis,we have prepared severalα-Fe₂O₃ nanostructures.The morphologies and microstructures of the materials are investigated in detail.And their electrochemical performance are also studied.The main contents are as follows:（1）The grain-likeα-Fe₂O₃ nanomaterials are prepared by a hydrothermal route.The growth mechanism of the material was explored by conducting comparative tests by using different solution compositions.And their microstructures are studied by a series of characterization means.The as-synthesized products are utilized as supercapacitor electrodes,The maximum energy density of 30.625 W h/kg can be achieved at a current density of 0.75A/g and the power density is 750 W/kg.（2）α-Fe₂O₃ nanorod arrays are grown on the surface of a flexible carbon cloth by a hydrothermal method.Then a layer of carbon film is covered on the surface of precursor.Theα-Fe₂O₃/C material delivers a specific capacitance of 280 F/g at 1 A/g.After 9000 cycles,the capacitance retention rate is 90.9%.A asymmetric supercapacitor with a working voltage of 2.0V is constructed withα-Fe₂O₃/C composite as negative electrode and MnO₂ nanosheet as positive electrode,which maximum energy density is 30.625 W h/kg.Capacity retention rate is82.1%after 10000 cycles.（3）α-Fe₂O₃ nanospindles are successfully prepared by a facile solution strategy.and the size and morphology of the as-obtained products are tailored by introducing different quantities of phosphate and sulfate ions.And the samples are coated with a thin layer of graphene by secondary hydrothermal approach.The as-obtained composite shows an electrochemical performance with a specific capacitance of 455 F/g at 1 A/g.The capacitance retention reaches87.5%after 10000 cycles.A quasi-solid asymmetric supercapacitor is assembled usingα-Fe₂O₃/rGO composite as the negative electrode and NiCo₂O₄ nanowire as the positive one.The device exhibits excellent supercapacitor performance with a maximum energy density of73 W h/kg at a power density of 1357 W/kg and the capacitance retention is 79.9% after 6000 cycles.