연근형 산화니켈-탄소 나노섬유로 제조한 슈퍼커패시터 전극재료 연구

Abstract

Highly porous and lotus-root-typed (LRT) nickel oxide-carbon (NiO/C) nanofibers are prepared by simple and cost-effective electrospinning process with bicomponent polymers of polystyrene (PS) and polyacrylonitrile (PAN). Nickel oxide (NiO), as one of the relatively few p-type semiconductor oxide materials, has recently received considerable attention because of its attractive applications in diverse fields. Nanostructured NiO is generally required, due to the advantage of high surface area to enhance chemical/electrochemical applications. Therefore, the preparation of nanostructures of NiO have attracted much attention for good photocatalytic properties in various energy storage devices. Electrospun biopolymer nanofibers were pyrolyzed with two stages at 250℃ for 2 hours in air and then 500℃ for 1 hour in nitrogen atmosphere, respectively. During carbonization, unstable PS played a critical role in forming the nanoporous LRT structure by acting as a sacrifice materials which providing additional formation of inner-pores and outer-etched-surfaces. It demonstrated outstanding electrochemical performances toward pseudocapacitive reactions. This is ascribed to highly meso and macro-porous large surface area of LRT NiO/C nanofibers with a large pore volume to support ion transfer and numerous surface active sites for pseudocapacitive reactions. Especially, the electrochemical properties of LRT NiO/C nanofibers depended strongly on the synthetic conditions in carbonization such as annealing temperature and time, which induced the synergic effect between atomic NiO and carbon frame. The electrode fabricated by the LRT NiO/C nanofibers showed the highly reversible specific capacity, good capacity-retention in supercapacitor, and high rate capability. The result obtained in this thesis revealed that the LRT NiO/C nanofibers have sufficient potential for the electrode material in supercapacitor applications.