Electrochemical impedance behavior of glass wool-based supercapacitors with different concentration of sulfuric acid

The paper presents the electrochemical impedance behavior of recently introduced corrosive resistant material for supercapacitor's separator; glass wool under four different concentration of 0.5, 1, 5 and 18 mol/dm3 sulfuric acid (H 2 SO 4 ) electrolytes. Ultracapacitors with a pair of activated carbon sheets as the active electrodes and each electrolyte-containing glass wool as the separator were constructed in a custom-made two-electrode test cell. The electrochemical impedance was carried out within the frequency range of 1 mHz to 100 kHz. The impedance data were extracted into a typical Nyquist plot, complex capacitance and complex powers in order to thoroughly evaluate the supercapacitors performance in terms of their specific capacitance, associated resistances, relaxation time and power capacity. Appealingly, as compared to the lower concentrated electrolyte-based supercapacitor, the supercapacitor with 18 mol/dm3 H 2 SO 4 electrolyte has outperformed others with 18% increment of specific capacitance, 57% enhancement of relaxation time and 63% reduction of internal series resistance. Overall, the electrochemical impedance behavior of the glass wool-based supercapacitors approach closely to an ideal capacitive characteristic under various H 2 SO 4 concentration, indicating its high potential to be applied in higher performance supercapacitor construction.