Electrochemical impedance spectroscopy (EIS) is a widely used analytical technique in electrochemistry and physics to study the electrical properties of conductive materials and their interfaces. It investigates ion diffusion, electrochemical reactions, and charge transfer in energy storage systems. The technique involves collecting EIS data with a potentiostat/galvanostat and fitting it to an equivalent electrical circuit to interpret charge and mass transport processes using Nyquist or Bode plots. Randles equivalent circuits are frequently employed to represent these processes. However, many studies do not adequately justify parameter values or achieve precise fittings, resulting in misleading interpretations. This review discusses the principles, applications, and theoretical background of EIS, focusing on layered materials. It highlights the significance of impedance definitions, data validation, and simulation in ensuring accurate analysis. The content aims to assist readers in understanding and applying EIS effectively.
Das et al. (2025) studied this question.