In the literature, it is widely stated that linearity is a necessary condition for accurate EIS measurements, but there are inconsistencies in terminology which should be clarified . First, it must be emphasized that there is a fundamental difference between the linearity of the current versus overpotential relation (i.e., the kinetics), and the linearity of the impedance signal (i.e., the measurement). Additionally, the term "non-linearity" has been used in the literature to describe both kinetics for which the current versus overpotential relation is exponential, or for which the current versus overpotential relation is asymmetric between the anodic and cathodic directions. For clarity, we refer to the former case as non-linearity, and the latter case as asymmetry. Both non-linearity and asymmetry of the kinetics can, but do not necessarily, result in a non-linear impedance signal . Likewise, it is possible for the impedance signal to contain significant non-linear contributions even if the kinetics are linear and symmetric . To measure the interfacial kinetics with EIS at high current densities, it must therefore be ensured that the impedance signal is sufficiently linear even though measurements are conducted within the non-linear region of the kinetics.