Cycling Stability Depends Closely On Scan Rate: The Case Of Polyaniline Supercapacitor Electrodes

Cycling stability of electrodes is a key performance index that determines the working life of supercapacitors. However, unlike specific capacitance and coulombic efficiency, nearly all researches in the literature report the cycling performance of electrodes with only one cyclic voltammetry (CV) scan rate/galvanostatic charge/discharge (GCD) current density, which is highly likely to overestimate the cycling stability. In this work, we investigate the dependence of cycling stability on CV scan rate, with polyaniline electrodes as examples. Our systematic experimental measurements show that scan rate has a marked effect on capacitance retention of the electrodes. A low scan rate leads to unsatisfactory cycling performance, while a high scan rate gives excellent data. The results can be understood with the aid of scanning electron microscope images. It is recommended that cycling performance of the PANi electrodes should be tested at relatively low CV scan rate/GCD current density, so as not to report an overestimation.