AN INVESTIGATION ON ELECTROCHEMICAL PERFORMANCE OF SUPERCAPACITORS ASSEMBLED WITH VERTICALLY ALIGNED&ENTANGLED CARBON NANOTUBE AND CONDUCTIVE POLYMER
Material Science and Engineering, PhD Dissertation, 2016
Thesis Jury: Asst. Prof. Dr. Fevzi C. Cebeci (Thesis Supervisor), Assoc. Prof. Selmiye Alkan Gürsel, Assoc. Prof. Kürşat Şendur, Assoc. Prof. Murat Ateş, Assoc. Prof. Musa Mutlu Can
Date&Time: February 22th, 2016 – 2 pm
Place: SUNUM G111
Keywords: Supercapacitor, vertically aligned carbon nanotube, entangled carbon nanotube, conducting polymer, electrochemical characterization, morphological characterization
Supercapacitors or electrochemical double layer capacitors are one of the most important research topics in the energy storage field because they fill the gap between batteries and commercial electrostatic capacitors. Long cycle life, high specific power density and short charge/discharge time offer advantages to supercapacitors over batteries; however, specific energy density of batteries is clearly higher than that of supercapacitors.
After introduction of multi-walled carbon nanotubes (MWCNT) to the scientific community by S. Iijima, carbon nanotubes (CNT) became a very popular electrode active material in supercapacitor applications because of its well-defined porosity, high surface area, chemical stability, and more importantly its high conductivity that might lead high power density. These characteristics are essential for high charge storage which is called double-layer capacitance. Two forms of CNT, which vertically aligned carbon nanotubes (VA-CNT) and the other one is entangled carbon nanotubes (EN-CNT) can be used as an electrode material in supercapacitors.
Implementing CNT with a conducting polymer which will give additional charge storage, called pseudo-capacitance, into a supercapacitor electrode structure ensures to achieve enhanced capacitive behavior. The reason of this is that supercapacitor will store the charge physically in the double-layer and also chemically in the polymer in this way. Among all conducting polymers, polyaniline (PANi) has been studied extensively due to its high conductivity, high theoretical capacitance, good faradic redox reversibility, and high stability in air and solutions.
In the present work, VA-CNT were synthesized by thermal chemical vapor deposition (CVD) on the silicon wafer. Free standing EN-CNT film without any binder was prepared from VA-CNT. Hybrid supercapacitor electrodes were fabricated via electrochemical and chemical methods. Electrochemical performances of the supercapacitor cells were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge tests in aqueous acidic electrolyte and organic electrolyte.