Review—Influencing Factors and Suppressing Strategies of the Self-Discharge for Carbon Electrode Materials in Supercapacitors

Supercapacitors, with the merits of high-power density, long durability, and remarkable safety, have already been used in the field of fast energy storage and conversion. However, their rapid self-discharge with spontaneous voltage decay results in the fast loss of the stored electric energy, severely limiting their practical application. Carbon materials have been widely used as the electrode materials for supercapacitors because of their large surface area, well-developed porous structure, and low-cost. Therefore, it is of great significance to understand the mechanisms and influencing factors, and further explore efficient suppressing strategies of the self-discharge behavior of carbon electrodes. In this review, we first introduce the self-discharge mechanisms including charge redistribution, Faradic reaction, and ohm leakage. Then, the key properties of porous structure, surface states, and metal impurities of carbon materials on the self-discharge behavior are discussed. Finally, we summarize some novel suppressing strategies and give perspectives on the future development of supercapacitors. This review provides an insight on the self-discharge of carbon-based supercapacitors, and can help to facilitate their widespread application.