The self-discharging of supercapacitors interpreted in terms of a distribution of rate constants

Abstract

Supercapacitors are prone to self-discharging, which is most often measured as a voltage decrease with time under open circuit conditions. It is of substantial interest to find simple and general methods to extract information about the processes going on in the supercapacitor during self-discharge. The current work fits a stretched exponential function to experimental data available in the literature, thus extracting parameters that allows one to probe the internal processes of the supercapacitor. In particular, experimental data related to charge holding time, charging rate before self-discharge and temperature dependence are investigated. It is demonstrated how the fitting data can be understood in terms of a kinetic model exhibiting a distribution of rate constants which are related to the fitting parameters. The current work therefore proposes a method that allows one to quickly map the internal processes of a self-discharging supercapacitors with only two variables, and might therefore become a useful tool.