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 (CO2). The electrochemical characteristics for EDLCs (region of ideal polarizability, characteristic time constant, specific series and parallel capacitances) are significantly dependent on the CO2 activation extent of the SiC-CDC materials. The calculated coulombic efficiency values for CO2 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 CO2 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 CO2 activation extent on the stored specific energy and specific power values delivered. (C) 2016 The Electrochemical Society. All rights reserved.