Development and characterization of carbon-based electrode materials and their implementation in supercapacitors
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Supercapacitors are energy storage devices, in which storage of energy is based on the formation of electric double layer at the interface of electrode and electrolyte. In gen-eral, a porous structure of electrode is needed to increase the surface area for formation of the electric double layer. The focus of this work was to design flexible supercapacitors, based on printing of dif-ferent carbon-based inks. Three classes of materials were tested: activated carbon (AC), graphene, and carbon nanotubes (CNT). A precondition of the work was to use envi-ronmentally friendly aqueous electrolyte. A problem arising from the use of aqueous based electrolytes is the corrosion of current collectors. Therefore, the aim was to elimi-nate the corrosion of metallic current collector. This was done by changing the superca-pacitor structure. The electrodes were fabricated on flexible polyethylene terephthalate (PET)-based substrates by blade coating. The supercapacitors were electrically characterized using the IEC 62391-1 international standard. From the galvanostatic charge-discharge measurement, capacitance values and equivalent series resistance (ESR) were measured. In addition, cyclic voltammetry (CV) was utilized to study the general behavior of supercapacitors. Moreover, the specific surface area (SSA) of electrodes was obtained from Brunauer, Emmett, and Teller (BET) method. The highest specific capacitance was obtained from activated carbon electrodes with values of 33 F/g. The SSA of AC was 1741 m2/g, which indicates that AC electrode material compromise a high concentration of pores. The specific capacitance obtained from CNTs was small, with the highest value of 5 F/g. Therefore, further development of CNT inks is necessary in order to make them a successful candidate as the electrode of printable supercapacitors. Moreover, ESR was primarily minimized by a suitable combination of electrode and current collector taking account of the corrosion risk caused by aqueous electrolyte.