Interpretation of Complex Capacitance Using Equivalent Circuit Involving Constant Phase Element

Abstract

An electrochemical impedance spectroscopy (EIS) is powerful tool to evaluate the electrochemical parameters of inside the energy conversion devices. The electric-double layer capacitance C dl can be estimated by the curve fitting of the impedance spectrum generally. It is important to obtain the C dl of the electrode because it is related to the surface area and structure of electrode/electrolyte interface. The performance of energy conversion devices can be investigated by the capacitance plots calculated from the impedance. (1-5) Our group (6) previously reported the calculations of the electrochemical impedance and complex capacitance corresponding to typical equivalent circuits involving a transmission line model (TLM) in order to determine the precise value of the C dl of electrochemical capacitor. In the present work, theory of complex capacitance were summarized by calculations using equivalent circuits. The complex capacitance calculated by equivalent circuit involving the constant phase element (CPE) was also discussed theoretically.