Development of an equivalent circuit model for electrochemical double layer capacitors (EDLCs) with distinct electrolytes

• Published in: Electrochimica acta Vol. 115; pp. 587 - 598
• Main Authors: Kang, Jinhee, Wen, John, Jayaram, Shesha H., Yu, Aiping, Wang, Xiaohui
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2014
• Subjects: Capacitors; Devices; Double layer; Electrical double layer capacitor; Electrochemical impedance spectroscopy; Electrodes; Electrolytes; Equivalent circuit model; Equivalent circuits; Equivalent series resistance; Impedance spectroscopy; Mathematical models; Potential dependency of impedance; Electrical double layer capacitor; Impedance spectroscopy; Equivalent series resistance; Equivalent circuit model; Potential dependency of impedance
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2013.11.002

An equivalent circuit model for electrochemical double layer capacitors (EDLCs) is proposed through analyzing the electrochemical impedance spectroscopy (EIS) measurements. The model is developed based on the Grahame theory, while these capacitive or resistive behaviors in the presence of charge diffusion and the ion adsorption at the double layer interface and bulk media are investigated. This circuit model, upon its validation against the EIS data, is successfully applied to characterize the practical EDLC devices. Meanwhile, experimental results are obtained from different EDLC cells that consist of the activated carbon-based electrodes and two electrolytes, namely, aqueous (H2SO4) and organic (Et4NBF4/PC). The model predicts the useful parameters (such as resistance and capacitance) which help interpret electrochemical reactions at the electrode/electrolyte interface. The quantitative dependence of impedance on the applied electrode potential is analyzed for two electrolytes during charging/discharging, and its correlation with the internal resistance (referred ESR) is studied.