Impedance spectroscopy became very popular among electrochemists ever since most modern potentiostats started incorporating hardware for collecting impedance and software, for interpretation of putative equivalent circuits. The popularity stems both from usefulness of the method, when judiciously applied, and from the ease to obtain graphs suitable for pondering their meaning. In fact, the method became so commonplace that it acquired the acronym EIS which electrochemists somewhat vainly explain as the electrochemical impedance spectroscopy even though in many situations, it is spectroscopy just electrical as there may not be electrochemical processes even going on.
The current turnkey potentiostats give capable electronic instrumentation to hands of people who do not need to be experts in electronic circuitry. This can lead to overinterpretation of data, particularly at higher frequencies. We will show on a case study how real-life input impedance of the instrument, which is typically and often successfully, ignored in data interpretation, can contribute to appearance of additional elements in fitted equivalent circuits.
With the turnkey hardware is also provided powerful software as a tool for assignment of physical or chemical properties of the studied sample. On a case study of a dielectric electronic material with a leakage we will show how interpretation with overlooked leakage contribution leads to incorrect interpretation of material permittivity, indicating its frequency dependence.
The attached figure shows impedance response of an active mass in a lead-acid battery studied for purpose of modern application for energy recuperation. This is one data set for an active lead acid mass 80 % discharged from a series of a full set of 0-100% discharged and 0-100% charged steps. The interpretation complication arises from the high frequency data (emphasized in the inset), where an inductor as an element in equivalent circuit might be called for. We will demonstrate how this response can be contributed to the real-life behavior of the impedance analyzer itself.