Charge-discharge cyclability of ultracapacitor with glass wool separator under high concentrated sulfuric acid

Abstract

The paper evaluates the charge-discharge cyclability of ultracapacitor with glass wool separator under various concentration of aqueous sulfuric acid (H2SO4) electrolytes. For lower concentrated electrolyte of 1 mol/dm3 H2SO4, the performance was compared to an ultracapacitor with conventional cellulose separator. Two-electrode ultracapacitors were constructed by sandwiching two activated carbon electrodes with each electrolyte-containing separator material. The cyclability test was performed with constant charge-discharge current of 10 mA for up to 300 cycles. Prior to the cyclability test, the constructed ultracapacitors were evaluated based on cyclic voltammetry and galvanostatic tests. The glass wool-based capacitor has performed comparably to the conventional cellulose-based capacitor in terms of its specific capacitance and internal resistance for up to 300 cycles. Interestingly, in a higher concentrated electrolyte of 18 mol/dm3 H2SO4, the specific capacitance of the glass wool-based ultracapacitor is 40% greater than of 1 mol/dm3 H2SO4 electrolyte. It is envisaged that by applying the glass wool as the separator coupled, with high concentration aqueous electrolyte may lead to higher rating ultracapacitor at relatively lower cost as compared to an organic electrolyte-based ultracapacitor.