*2.1. Experimental Setup*

The dynamic behavior of symmetric double-layer UC (BCAP3400: 3400 F, 2.85 V [34]) was investigated using the electrochemical impedance spectroscopy (EIS), and repetitive charge-discharge cycles. Figure 1a,b demonstrate the experimental setups, and detailed descriptions of experimental setups were discussed in our previous article [13]. For charge-discharge cycle experiments, a charge/discharge system controller [35], regulated DC power supply [36], electronic load [37], and midi-logger GL900 [38] were used. A constant repetitive pulsed current (50 A) was applied for both charge-discharge cycles. The constant current was applied for two seconds, with an interval of two seconds. The internal resistance and capacitance were calculated using the typical voltage vs. time curve for the discharging process [13]. The EIS investigations were performed using the EchemLab XM potentiostat-galvanostat analyzer [39] and Tenney temperature test chamber [40]. The EIS experiments were performed with an AC current of 1 A (rms) and frequencies of 1 Hz–1 kHz.

**Figure 1.** (**a**) Experimental setup for the charge-discharge cycles (1-charge/discharge system controller, 2-regulated DC power supply, 3-electronic load unit, 4-midi-logger, and 5-capacitor). (**b**) Experimental setup for the EIS measurement (1-Potentiostat-galvanostat, and 2-Tenneytemperature test chamber).
