Review - Mitigating Supercapacitor Self-Discharge through Strategic Materials Modification

A high-power density, rapid charge-discharge and long cycle life are important features of supercapacitors (SCs). However, SCs are mainly suffered from their high self-discharge (SD) which is a spontaneous decay of voltage with time under open-circuit conditions. Due to SD behavior, SCs cannot be employed or coupled with many important energy harvesting devices including piezoelectric and triboelectric nanogenerators. It is highly desired to develop different innovative strategies to mitigate the SD. This review aims at discussing a SD mechanism and reviewing different mitigation strategies based on the modification of materials and devices. We discuss design, underlying principle, mechanism of the mitigation strategies and corresponding SD performance in detail. Moreover, the summary and prospects in this field have been provided. It is recommended to test an individual electrode for SD, identify the mechanism and develop different strategies for suppression. This review will be beneficial for researchers around the world to have a better understanding of the SD mechanism and to develop innovative strategies for SD mitigation and thereby the high-performance SCs.