Preparation And Characterization Of Metal Oxide/C&S Composites And Their Application In Supercapacitor

As an electrical energy storage device,supercapacitors have the advantages of fast charging speed,high energy and power density,long cycle life and environmental friendliness.Supercapacitors have been applied in many fields,such as electric vehicles,consumer electronics,military,solar and wind power generation.As an important part of supercapacitor,electrode materials have attracted significant research focus in chemistry,material sciences,and other fields.In this thesis,some metal oxide composites doped with C and S were fabricated to exploit the advantages of both oxides and carbon-based materials.When used as supercapacitor electrodes,the synthesized composites show extra-long cycling stability during the charge/discharge process.The specific contents are listed as below:?1?A cobalt coordination precursor was synthesized with glucosinolates salicylic acid and cobalt salt,and Co₃O₄/C&S nanocomposite was fabricated by sintering the precursor at different temperature.The structure,morphology and electrochemical properties of electrode materials under different calcination temperatures are studied.The results show that the sample sintered at 400?had the best electrochemical performances,its specific capacitance is 142.45F/g at the constant charge/discharge current of 1A/g,and 99.67%of its initial specific capacitance remained after 20,000 cycles.The as-prepared composite exhibits much more stable cycling stability during the charge/discharge process.?2?A cobalt/nickel coordination precursor was synthesized with the glucosinolates salicylic acid,cobalt salt and nickel salt.A tightly packed Co₃O₄/NiCo₂O₄/NiO/C&S nanocomposite was fabricated by sintering the Co/Ni-based coordination complex precursor at 400?.The composites with different molar rations of cobalt and nickel are characterized using various techniques,namely,X-ray powder diffraction,scanning electron microscopy,transmission electron microscopy,Brunauer-Emmett-Teller specificsurfaceareaanalysis,andelementalanalysis.The electrochemical performance was analyzed by cyclic voltammetry,galvanostatic charge/discharge cycling,and electrochemical impedance spectrometry.The electrochemical properties showed that the samples with Co:Ni=1:4 had the highest capacitance?536 F/g at 1A/g?compared with the other samples,and 100%of its initial specific capacitance remained after 5000 cycles at 3A/g.The results show that a supercapacitorwithelectrodesmadefromtheas-prepared Co₃O₄/NiCo₂O₄/NiO/C&S composite will be promising for commercial applications.?3?By simple chemical precipitation method,two kinds of cobalt hydroxides and nickel hydroxides doping with different sulfur sources were synthesized.Two kinds of Co₃O₄/S and NiO/S nanocomposites were fabricated by sintering the two kinds of cobalt hydroxides and nickel hydroxides at 400?.Their composites were characterized and their electrochemical performances were also analyzed.The electrochemical properties showed that the samples of Co₃O₄/S doping with Na₂SO₃ and NiO/S doping with Na₂SO₄ had the highest capacitance?280F/g and411.54F/g at 1A/g?,and 88.24%and 82.39%of their initial specific capacitances remained after 20000 cycles and 5000 cycles at 3A/g,respectively.The cycle life and specific capacitance are both improved comparing with pure Co₃O₄ and NiO samples.