Revisiting the Analysis on Charge Redistribution of Supercapacitors

Supercapacitors (SC) are high energy electrochemical capacitors, which are being widely employed for replacing or assisting batteries in several applications. The capacitance value of these SCs shows substantial variation with operating conditions owing to porous nature of their electrodes. Porosity of the electrodes provides higher surface area and in turn higher capacitance. However, the complete surface is not accessible immediately and hence charges redistribute throughout the surface during charging and the rest time. This charge redistribution is highly nonlinear and its characterization is essential for optimizing the SC system design. This paper presents a comprehensive analysis on the charge redistribution models and characteristics based on the experiments conducted on several commercial supercapacitors. The dependence of the charge redistribution on the voltage level, current, cycle number and residual charge is illustrated. Further losses associated with charge redistribution and their applications are analysed. The new observations and interpretations on the charge redistribution of supercapacitors are finally summarized and guidelines on optimizing the charging of SC systems are provided.