Performance of Electric Double Layer Capacitors with Gel Electrolytes Containing an Asymmetric Ammonium Salt

Abstract

Polymer gel electrolytes, composed of poly(vinylidene fluoride) (PVdF) and propylene carbonate (PC) as a plasticizer with the asymmetric ammonium salt triethylmethylammonium tetrafluoroborate (TEMABF₄), have been applied to electric double layer capacitors (EDLCs) with activated carbon cloth electrodes. The present capacitors with TEMABF₄ have a higher capacitance, better coulombic efficiency, and lower leak current than those with a typical electrolytic salt, tetraethylammonium tetrafluoroborate (TEABF₄). Ac impedance measurements show that the capacitors with TEMABF₄ have not only lower electrolyte-bulk resistances but also lower electrolyte/electrode-interface resistances in comparison with the capacitors with TEABF₄.