Impedance spectroscopy is a versatile, powerful and non-destructive analysis technique for material characterization. It is applied for instance for the investigation of dielectrics, passivation effects, redox reactions or even of fully assembled batteries. With alternating current (AC) measuring frequencies ranging from MHz down to mHz, EIS allows for studying processes taking place on timescales from microseconds up to hours or even days.
One of the biggest challenges in practical impedance spectroscopy is the analysis of the measured data in a physically meaningful way. The analysis is complicated by the fact, that most electrochemical systems do not consist of a homogeneous phase in contact with the electrodes, but of a lot of different phases with phase boundaries between them. For example, a typical 2-electrode impedance spectrum of a battery will show contributions of every material, interface and electrode reaction inside the cell. To distinguish between individual impedance contributions, electrochemical experiments are often carried out in a 3-electrode setup. But why and how can this help?
This application note will focus on answering this question both from theoretical considerations and simulation as well as with practical experiments.
To cite this application note, please use: “Wallauer et al., rhd instruments GmbH & Co. KG, Application Note: 2-electrode and 3-electrode setups – A comparison of experiment and simulation, November 2020”.