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

This study demonstrates the criteria for determining the working potential window of commercial activated carbons (ACs) in the propylene carbonate-based (TEABF(4)/PC) electrolyte for electrical double-layer capacitors (EDLCs). Through a common potential-floating examination, the working potential window of ACs in 1 M TEABF(4)/PC is between -2.0 and 03 V (vs. Ag/AgNO3). However, an EDLC consisting of the above ACs in 1 M TEABF(4)/PC with charge/discharge in this potential window for 1152 cycles 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 0.2 V, 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 10,000 cycles. The EIS results also reveal an acceptable capacitor behavior after the 10,000-cycle CD test. (C) 2016 Elsevier B.V. All rights reserved.