Electrochemical impedance spectroscopy for different types of supercapacitors

Electric Double Layer Capacitors (EDLCs) are relatively new electronic components developed in the late 1980s; their operation is based on a Helmholtz double layer of charge formed on an activated carbon surface (of high equivalent surface) and an electrolyte. The advantages of this constructive solution are a very small capacitive distance and large effective capacitive area, leading to remarkably large capacitances. EDLCs tend to be low voltage, low impedance devices, sustaining high currents, and with a capacitance dependent on the charge-up voltage. In this context it is important to accurately know their parameters in order to design the associated circuitry - in particular of interest are values for equivalent series resistance (ESR) and parallel resistance (self-discharge) of the EDLC. The results presented in this paper are focused on a comparison between using the electrochemical impedance spectroscopy (EIS) method and the direct method (DM) in determining super capacitor parameters. This comparison was performed in the 10
^-
... 10
⁵
Hz range, albeit (due to parasitic components) only the 10
^-
...10
³
Hz range is effective.