An approach to unify capacitance measurements of electric double layer capacitors using sinusoidal potential scan

Measuring supercapacitor capacitance is essential to understanding their electrical characteristics. However, different techniques can provide significantly different capacitance values. This discrepancy makes it difficult to compare results and communicate new research findings, hindering the progress of supercapacitor technology, particularly electric double layer capacitors (EDLCs). Voltammetry techniques often assume an ideal capacitor, while electrochemical impedance spectroscopy (EIS) recognizes the need to model the non-ideal electrode behavior with a constant phase element (CPE). Through comparison with the responses of two commercial EDLCs, this study confirms that the time domain responses of EDLCs should be modeled with CPE rather than a pure capacitor. The derived equations are then used to examine the effects of experimental conditions and the CPE exponent on capacitance measurements in cyclic voltammetry (CV). The study shows that estimated capacitances are affected by several experimental conditions, not only the scan rate, highlighting the need for an alternative approach to unify the capacitance measured using different analytical methods and measuring techniques. Therefore, this study proposes an alternative approach to estimate the capacitance of a CPE using a sinusoidal potential scan in voltammetric measurements. This approach not only equalizes the capacitance measured using different analytical methods and measuring techniques but also significantly reduces the number of experimental parameters affecting the calculated capacitance to just the frequency (or scan rate). The findings of this study offer valuable insights into the estimation of capacitance via various methods and have potential implications for improving the performance of electrochemical devices, particularly EDLCs, in the pursuit of a clean energy future.