Comparison of methods for finding the capacitance of a supercapacitor
L. E. Helseth
Abstract
A carbon-based supercapacitor is usually associated with a capacitance such that the user can access its ability to store electrical charge. Three different measurement methods or variations thereof are typically employed to find the capacitance; galvanostatic charging, cyclic voltammetry and impedance spectroscopy. These three methods may give rather different capacitances, which must be interpreted with care. Here, it is discussed how one can extract consistent capacitance values from measurements obtained with the three techniques, to be interpreted within a single dynamic equivalent circuit. Different methods are compared in order to demonstrate where systematic errors occur, and how and under which conditions they can be removed. The extension of the methods presented here to pseudocapacitors utilizing both Faradaic and non-Faradaic charge storage is also briefly discussed.