Potential-Dependent Electrochemical Impedance Spectroscopy as a Powerful Tool for Evaluating Supercapacitor Electrode Performance

Electrochemical impedance spectroscopy (EIS), an alternated current measurement, is a powerful technique that can be used to distinguish the different charge storage mechanisms. In addition, EIS allows quantification of the electrode performance. However, the utilization of potential-dependent EIS measurements is more convenient to explore electrochemical phenomena occurring at the electrode interface. Herein, we discuss the advantages in using multiple polarized EIS for performance evaluation of three classical electrode types: capacitive, pseudocapacitive, and battery-like, employed in supercapacitor devices. The results are compared with those obtained by direct current methods displaying good agreement in the case of capacitive electrodes. On the other hand, pseudocapacitive and battery-like electrodes exhibit strong ohmic effects and non-reversible processes when the power law equation is utilized. Both of these issues can be circumvented by using potential-dependent EIS.