Manufacture Of Supercapacitor Based On One-dimensional Nanostructured Materials

With the increasingly serious environmental pollution,energy crisis and the requirements of sustainable development,new green and sustainable energy storage technologies are required.As a new type of electrochemical energy storage device,supercapacitor has attracted extensive attention.Transition metal oxides used as electrode materials of supercapacitors can not only provide higher specific capacitance than traditional carbon materials,but also have better electrochemical stability than polymer materials.However,the supercapacitors have the disadvantages of poor rate performances and bad cyclic stability in practical application.Therefore,it has become one of the frontier and hot research directions in the field of energy storage to improve the performances of supercapacitors via rational design and preparation of electrode materials with unique structures.In this dissertation,NiO nanowire-in-nanotube@PPy,Sn O₂@WO₃heterostructure nanocomposite fibers and Co₃O₄@Bi₂O₃core-shell nanocomposite fibers are designed and constructed,and further,their structures,morphologies and electrochemical properties are detailedly studied.The details are as follows:1.The NiO nanowire-in-nanotube@PPy nanofibers were fabricated by electrospinning combined with gas phase polymerization.The NiO nanowire-in-nanotube in the core layer can provide relatively high specific capacitance due to its large specific surface area,the PPy in the shell layer can provide effective electron transfer paths and additional pseudo-capacitance to improve the electrochemical performances of the bare NiO wire-in tube.In three-electrode system,NiO nanowire-in-nanotube@PPy nanofibers are used as the working electrode of the capacitor,the specific capacitance is 205 F g^-1when the current density is 1 A g^-1.After 1000 cycles of charge and discharge at 5 A g^-1,the retention rate of the initial capacitance is about 80%.2.The Sn O₂@WO₃heterostructure nanocomposite fibers were fabricated by coaxial electrospinning followed by subsequent calcination process.The Sn O₂nanofibers in the core layer of the material can provide a fast channel for the transmission of electrolyte ions.The WO₃nanoparticles in the shell layer uniformly anchored on Sn O₂nanofibers can effectively increase the specific surface area of the material,which facilitates the electron transfer in the Faraday pseudo capacitance reaction,thus producing high specific capacitance.In three-electrode system,Sn O₂@WO₃heterostructure nanocomposite fibers are used as the working electrode of the capacitor,the specific capacitance is 287.5 F g^-1at the current density of 1 A g^-1.After 2000 cycles of charge and discharge at 5 A g^-1,the retention rate of the initial capacitance is about 91.2%.3.The Co₃O₄@Bi₂O₃core-shell nanocomposite fibers were fabricated by the combination of coaxial electrospinning with following calcination process.The Co₃O₄nanofibers in the core layer have high internal resistance,which limits the electron transport in the material and leads to low capacity.However,the Co₃O₄nanofibers exhibit good cycling stability in the capacitor.The Bi₂O₃nanofibers in the shell layer have a wide potential window and a high specific capacity.Therefore,the nanocomposite fibers have high specific capacitance and good cycling stability.In three-electrode system,Co₃O₄@Bi₂O₃core-shell nanocomposite fibers are used as the working electrode of the capacitor,the specific capacitance is as high as 341 F g^-1at the current density of 1 A g^-1.After 2000 cycles of charge and discharge at 5 A g^-1,the retention rate of the initial capacitance is about 88.5%.In this dissertation,three kinds of one-dimensional nanostructured materials are successfully constructed based on electrospinning technology and used as electrode materials of supercapacitors.Some meaningful research results are obtained,which provide a new idea for the development of electrode materials of supercapacitors in the future.