Binder-controlled pore size distribution of carbon electrodes to mitigate self-discharge of supercapacitors

Self-discharge, which refers to voltage depression when a power source is removed, is a crucial issue for supercapacitors (SCs). Self-discharge results in Coulombic efficiency loss and energy dissipation, and thus restricts the charge storage performance of SCs. A cost-effective and facile strategy for addressing self-discharge is newly developed in this work. It is found that self-discharge involves charge redistribution and Faradaic side reactions, which are closely associated with the pore size of activated carbon electrodes. Importantly, the pore size distribution (and thus self-discharge) can be controlled by the binder type. Specifically, a binder that maintains high macropore and mesopore fractions can effectively mitigate self-discharge. The fundamental reasons for this finding are examined. The effects of the charging rate, holding time at the full charging voltage, operation temperature, and charging cutoff voltage on the self-discharge of SCs prepared using various binders are investigated. The data reveal that binder selection also influences SC reliability in terms of the aging rate at elevated temperature and high voltage, leakage current, and gas evolution during operation.

Automated summary

Self-discharge is a crucial issue for supercapacitors, which results in voltage depression and limits their charge storage performance. A cost-effective and facile strategy for addressing self-discharge is developed in this work. It is found that self-discharge is closely associated with the pore size distribution of activated carbon electrodes, and this can be controlled by the binder type. The effects of binder selection on the self-discharge and reliability of supercapacitors are investigated.