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

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, we gives a timely spotlight on breakthroughs in the self-discharge mechanism investigations of supercapacitors and the corresponding suppression strategies. The self-discharge mechanisms of various 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.