The Pitfalls and Opportunities of Impedance Spectroscopy of Lithium Sulfur Batteries

Abstract Electrochemical impedance spectroscopy (EIS) is a valuable tool, which is frequently applied to study lithium‐sulfur (Li‐S) batteries. However, as shown in this perspective article, there are several pitfalls associated with the measurement parameters, impedance response interpretation, and spectra fitting, which can result in dubious or erroneous conclusions. In the first part, the available information on Li‐S battery impedance response is summarized and it is critically evaluated. The authors also touch on the methodology of measurements and fitting of impedance spectra, and later on systematically overview the impedance features in sections according to characteristic peak frequencies of processes, going from the highest to lowest. Finally, specific test instructions that ensure the use of EIS's full potential are listed and promising future directions are discussed. These range from an increase in the use of model experiments, replacement of arbitrary equivalent circuit fitting with physics‐based impedance models, and coupling of the technique with other analytical tools.