Insight into the self-discharge suppression of electrochemical capacitors: Progress and challenges

Abstract

The ever-growing demands for renewable energy sources motivate the development of energy storage systems. Among them, supercapacitors are received increasing attention due to their high power density, long cycle life, fast recharge rate, and almost no maintenance. Nevertheless, their application is hindered by severe self-discharge behaviors, especially in wearable and energy storage devices. In recent years, tremendous excellent works have been reported to conquer this shortcoming through various creative strategies. Herein, this article gives a timely spotlight on breakthroughs in the self-discharge mechanism investigation of supercapacitors and the corresponding suppression strategies. The self-discharge mechanisms of various types of supercapacitors were introduced first, followed by a summary of the strategies from materials (i.e., electrode, electrolyte, and separator) to system and protocol optimization. Furthermore, the connection between them, existing issues, and possible directions for future research are discussed. Supercapacitors are promising electrochemical energy storage systems but restricted by severe self-discharge issues. This work discusses the self-discharge mechanisms, including Ohmic leakage, Faradiac reaction, and charge redistribution. Besides, the corresponding suppression strategies for various supercapacitors are analyzed in detail. Further, the future research directions are pointed out towards practical applications. ● Supercapacitors are hindered by severe self-discharge behavior. ● Tremendous excellent works have been reported to tackle this shortcoming. ● The self-discharge mechanisms of supercapacitors are introduced. ● The progress on suppression strategies from materials to systems is reviewed. ● The remaining issues and possible strategies are highlighted.