Impact of the Scan Rate on the Stability Window of an Electrical Double-Layer Capacitor

Abstract

Because of the intermittent nature of renewable energy sources, such as solar or wind power, energy storage is becoming strategic for securing the energy transition. In this context, energy storage technologies must become robust, secure, and efficient, so that they become attractive and competitive solutions. For these reasons, the stability of storage systems is a matter which must concern us. In the supercapacitor community, methodologies used to evaluate the stability window are widely discussed and debated, but the way it is impacted by the charging regime is rarely investigated. This question is even more important as the stability window is only valid for the current rate at which it was determined. In this study, the impact of the charging regime on the stability window was investigated both qualitatively and quantitatively by cyclic voltammetry. Results clearly demonstrate that the stability window reduces as the scan rate decreases. This is because degradation processes can be viewed as the result of irreversible electrochemical processes. In severe cases, this reduction in stability is such that it can be fatal for the supercapacitor if such a change in the charging regime has not been anticipated.