Determination of the upper and lower potential limits of the activated carbon/propylene carbonate system for electrical double-layer capacitors

Abstract

This study demonstrates the criteria for determining the working potential window of commercial activated carbons (ACs) in the propylene carbonate-based (TEABF4/PC) electrolyte for electrical double-layer capacitors (EDLCs). Through a common potential-floating examination, the working potential window of ACs in 1M TEABF4/PC is between −2.0 and 0.3V (vs. Ag/AgNO3). However, an EDLC consisting of the above ACs in 1M TEABF4/PC with charge/discharge in this potential window for 1152cycles shows 27% capacitance loss. The electrochemical impedance spectroscopic (EIS) analyses show the presence of an obvious impedance arc behind the high-frequency semicircle on both positive and negative electrodes after the charge–discharge (CD) cycling. Consequently, a combination of a potential-floating test and EIS analyses precisely determines the working potential window between −1.9 and 0.2V, which is a reliable method to efficiently define the working potential window. In this potential range, an EDLC exhibits about 6% capacitance loss during the CD test for 10,000cycles. The EIS results also reveal an acceptable capacitor behavior after the 10,000-cycle CD test.