Role of textural properties and surface functionalities of selected carbons on the electrochemical behaviour of ionic liquid based-supercapacitors

Abstract

In the present study, five different activated carbons are used as active electrode materials in Ionic Liquid based-Supercapacitors (IL-SCs). Selection of carbons was made according to their different textural and surface properties and includes microporous, microporous–mesoporous and mesoporous carbons with specific surface areas (S_DFT) ranging from 1400 to 2200 m² g⁻¹ and pore lengths (L_o) ranging from 0.7 to 2.8 nm. These carbons are used to build IL-SCs using the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR₁₄TFSI) as the electrolyte. IL-SCs are electrochemically characterized by electrochemical impedance spectroscopy (EIS) and by galvanostatic charge/discharge (C/D) methods at 25 °C and at 60 °C. The effect of increasing the temperature and the voltage window on electrochemical performance is analysed. The performance of IL-SCs in terms of specific capacitance (C_s) and specific energy (E_real) strongly increased with temperature and with maximum voltage (V_max) reaching values as high as 245 F g⁻¹ and 58 Wh kg⁻¹ at 60 °C and 3.5 V. The influence of both textural properties and surface chemistry of the carbons on the performance of IL-SCs is analysed in detail.