Voltage‐Dependent Capacitance, Aging Effects, and Failure Indicators of Double‐Layer Capacitors during Lifetime Testing

Aging phenomena, which occur during long‐term cycling tests of supercapacitors, complicate the exact determination of comparable capacitance values by using hitherto introduced electrochemical techniques. The gradual degradation of polymer‐bound carbon electrodes during long‐term operation is caused by the destruction of the adhesive layer between the active material and current collector. Based on ten years of testing experience, a reliable voltammetric method is proposed, with which it is possible to distinguish useable capacitance, residual charges caused by chemical aging processes, and mechanical failure causes. The capacitance of electrode–electrolyte interfaces is shown as a function of temperature, frequency, voltage, state‐of‐charge, and the operating conditions.