Supercapacitors Based on Activated Silicon Carbide-Derived Carbon Materials and Ionic Liquid

Cyclic voltammetry, constant current charge/discharge, electrochemical impedance spectroscopy and constant power discharging methods have been applied to establish the electrochemical characteristics of electric double–layer capacitor (EDLC) consisting of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4 ) and micro/mesoporous carbon electrodes prepared from silicon carbide derived carbon (SiC-CDC) that have been additionally activated with carbon dioxide (CO 2 ). The electrochemical characteristics for EDLCs (region of ideal polarizability, characteristic time constant, specific series and parallel capacitances) are significantly dependent on the CO 2 activation extent of the SiC-CDC materials. The calculated coulombic efficiency values for CO 2 activated systems vary within the range from 97 to 99.8% (calculated using integrated charge density values). The energy efficiencies from 82 to 86.5% show that the CO 2 activated SiC-CDC powders are much more suitable for various power and energy storage applications compared to untreated SiC-CDC. From impedance spectroscopy the highest capacitance value of 170 F g −1 at 3.6 V has been established for SiC-CDC with the largest activation burn–off extent of carbon from SiC-CDC. The Ragone plots for the carbon materials synthesized show noticeable influence of the CO 2 activation extent on the stored specific energy and specific power values delivered.