An electrical double layer exists at the interface between an electrode and its surrounding electrolyte. This double layer is formed as ions from the solution “stick to” the surface of… read more →
A capacitor is formed when two conducting plates are separated by a non-conducting medium, called the dielectric. The value of the capacitance depends on the size of the plates, the… read more →
Capacitors in EIS experiments often do not behave ideally. Instead they act like a constant phase element (CPE) as defined below. The impedance of a CPE has the form: When… read more →
A similar resistance to electrolyte resistance is formed by a single kinetically-controlled electrochemical reaction. In this case we do not have a mixed potential, but rather a single reaction at… read more →
Signal-processing theory refers to data domains. The same data can be represented in different domains. In EIS, we use two of these domains, the time domain and the frequency domain.… read more →
Very few electrochemical cells can be modeled using a single equivalent-circuit element. Instead, EIS models usually consist of a number of elements in a network. Both serial and parallel combinations… read more →
Measuring an EIS spectrum takes time (often many hours). The system being measured must be at a steady state throughout the time required to measure the EIS spectrum. A common… read more →
Electrical circuit theory distinguishes between linear and non-linear systems (circuits). Impedance analysis of linear circuits is much easier than analysis of non-linear ones. The following definition of a linear system… read more →
EIS data are commonly analyzed by fitting them to a model of an equivalent electrical circuit. Most of the circuit components in the model are common electrical elements such as… read more →
Almost everyone knows about the concept of electrical resistance. Resistance is the ability of a circuit element to resist the flow of electrical current. Ohm’s law defines resistance in terms… read more →