Abstract
UDC 538.971
This work presents results of our research of the structure and properties of a nanocomposite material (NCM), the components of which include nanoporous carbon (NPC) and thermally exfoliated graphite (TEG). The NCM is to be used as electrode material for supercapacitors (SC) with a double electric layer. The NPC was obtained from a phytogenic raw material using hydrothermal carbonization. The TEG was produced from oxidized natural graphite by thermal exfoliation. A JSM-6490LV electronic microscope was used to study the samples microstructure; a Quantachrome Autosorb instrument was used to analyse the isotherm adsorption/desorption of nitrogen, that is, to analyse the porous structure; and a multipoint BET (Brunauer-Emmett-Teller) method was used to determine the electrode specific surface area. Both galvanostatic cycling and electrochemical impedance spectroscopy methods on AUTOLAB PGSTAT12 measuring instrument were used to analyze electrochemical properties of the samples. Our study shows that employment of TEG in this NCM makes the internal resistance of supercapacitors to decrease, thus causing an increase in their specific internal capacitance. The results of electrochemical studies show that the capacity of supercapacitors based on the above NCM is 155–160 F/g. An equivalent circuit is proposed, which allows modelling impedance spectra in the frequency range of 10-3–105 Hz. A physical interpretation of each element of the electric circuit is presented.
Keywords: nanocomposite materials, nanoporous carbon, thermally exfoliated graphite, supercapacitor, specific capacitance.