PEIS is used to measure 𝑅 𝑐𝑡 0 by applying a small amplitude voltage perturbation about the equilibrium voltage of the cell . The voltage perturbation should generally be limited to 5 -25 mV to maintain linearity of the impedance response . The interfacial charge-transfer resistance manifests as a semi-circle in the Nyquist plot, and the value of 𝑅 𝑐𝑡 0 can be calculated through conventional techniques, such as equivalent-circuit analysis or other graphical methods. PEIS provides two main utilities in the context of high current density electrochemical measurements.