Large Amplitude Electrochemical Impedance Spectroscopy for Characterizing the Performance of Electrochemical Capacitors

Abstract

Electrochemical impedance spectroscopy (EIS) has been applied to the study of electrodeposited thin films of manganese dioxide as used in electrochemical capacitors. Conventionally EIS employs a relatively small AC excitation signal to provide valuable characterization on electrode features such as the series resistance, charge transfer and double layer charge storage processes, as well as mass transport. The small excitation signal is used so as to focus on the processes occurring within that potential domain allowing for considerable resolution across the full potential window. In this work we have compared the output from this conventional analysis with data from the application of a large amplitude AC excitation signal; i.e., an AC signal that spans the full potential window of the manganese dioxide electrode. Not only does this allow access to electrochemical data representative of the full range of domains within the manganese dioxide structure, it also facilitates performance analysis (determination of specific power and energy data) of the electrode in a much more efficient manner than conventional means, as well as enables separation of the total specific capacitance into its non-faradaic and faradaic components.