Effect of cylindrical and prismatic configurations on supercapacitor self-discharge and their mitigation approach by external charging strategies

Supercapacitors with cylindrical and prismatic configurations exhibit notable differences in self-discharge performance. The experimental results reveal that prismatic supercapacitors demonstrate superior self-discharge performance than their cylindrical counterparts across various holding times. In fact, prismatic supercapacitors experience a smaller absolute voltage drop due to both Ohmic leakage and diffusion contributions when compared to cylindrical supercapacitors. For interpreting the differences in terms of Ohmic leakage and diffusion, the result of electochemical impedance spectroscopy reveals that the ratio of internal resistance between the cylindrical supercapacitor and the prismatic supercapacitor is inversely proportional to the ratio of absolute voltage drop due to Ohmic leakage. In addition, the results of numerical models for diffusion show that the reduced self-discharge observed in the prismatic supercapacitor is attributed to a smaller concentration gradient at the end of charging. Finally, mitigation of self-discharge for cylindrical and prismatic supercapacitors by external charging strategies is investigated. The results show that charging-holding-resting strategy exhibits the best self-discharge mitigation for cylindrical supercapacitors. On the other hand, both charging-holding-resting-discharging and charging-holding-resting strategies prove to be similarly effective in mitigating self-discharge for prismatic supercapacitors. This could serve as an external approach to effectively mitigate self-discharge of a supercapacitor with specific configuration.