Preparation Of Composites Based On Polydopamine And Its Capacitance Properties Research

Supercapacitor is a type of energy storage device with high power density,fast charging-discharging rate,and long lifecycle,etc.So,it has great application prospect.Electrode materials are the core of supercapacitor,and its performance and cost directly affect the application of supercapacitor.Therefore,it is the key to develop electrode materials with excellent performance and low price.In this paper,the composites of carbon materials and metal oxides are studied.On the one hand,the high conductivity and high cycle stability of carbon materials are used.On the other hand,high performance composites are prepared by using the high capacitance of metal oxides.The properties of the composites are improved by synergistic action.Polydopamine?PDA?was chosen as carbon materials,because there are many active groups on the surface of PDA,which have certain chemical activity and adsorb ability.In addition,they can be calcined into N-doped carbon spheres at high temperature.Thus,more active sites are provided.MnO₂,NiCo₂O₄ and Fe₃O₄ were selected because of their abundance,low cost and environmental friendly.The main research content was carried out from three aspects as follows:?1?Polydopamine and MnO₂ core-shell composites?PDA@MnO₂?were prepared by a facile and fast method.The morphology,crystalline phase and chemical composition of PDA@MnO₂ composites were characterized using SEM,TEM,XRD,EDS and XPS.The performance of PDA@MnO₂ composites were further investigatedbycyclicvoltammetry,galvano-staticcharge-dischargeand electrochemical impedance spectroscopy in 1 M Na₂SO₄ electrolyte.The PDA@MnO₂ core-shell nanostructure composites exhibited a high capacitance of 193F g^-11 at the current density of 1A g^-11 and retained over 81.2%of its initial capacitance after 2500 cycles of charge-discharge at 2 A g^-1.?2?PDA spheres were carbonized into N-doped carbon spheres?NCSs?at high temperature,and then NiCo₂O₄ nanosheets were grown on NCSs.Core-shell structure NCSs@NiCo₂O₄ composites were successful prepared.NCSs@NiCo₂O₄ composites had good capacitive properties.The specific capacitance of NCSs@NiCo₂O₄ could reach 983 F g^-11 at the current density of 0.5 A g^-1,and the electrochemical performance of NCSs@NiCo₂O₄ was much better than that of NiCo₂O₄.?3?The Fe³⁺in the FeCl₃ solution was adsorbed on the surface of the PDA spheres by using the adsorptive property of the PDA spheres,and then the NCSs@Fe₃O₄composites were formed by pyrolysis at high temperature.The specific surface area and pore size of the NCSs@Fe₃O₄ composites were increased.The NCSs@Fe₃O₄composites showed better electrochemical performance,with a specific capacitance of206 F g^-11 at current density of 1 A g^-1,and still keeping the initial capacity 95%after a cycle of 5000 loops.NCSs@Fe₃O₄//NCSs asymmetric supercapacitor was constructed using NCSs@Fe₃O₄ as cathode electrode material and NCSs as negative electrode material.It had a good electrochemical performance.