An rGO/cellulose acetate/PVDF piezoelectric separator for mitigating self-discharge in supercapacitor

Flexible, miniature, and lightweight supercapacitor is ideal power source for next-generation portable and wearable electronics. However, their widespread application is limited by a critical drawback, self-discharge, which leads to energy loss during idle periods. To this end, a polyvinylidene fluoride (PVDF)-based nanofiber separator with piezoelectric properties that can effectively suppress self-discharge in supercapacitors, was prepared via electrospinning. By incorporating hydrophilic cellulose acetate (CA) and reduced graphene oxide (rGO) into the PVDF matrix, both the electrolyte affinity and piezoelectric output of the separator are significantly enhanced. The resulting rGO/CA/PVDF composite membrane exhibits outstanding mechanical flexibility, high porosity, excellent electrolyte uptake, making it highly suitable separator for flexible supercapacitor. Supercapacitors equipped with such separator exhibit superior electrochemical performance with a specific capacitance of 178.2 F/g at 10 A/g. Notably, an impressive capacitance retention of 79 % was achieved after 24 h of self-discharge test. The reduction in self-discharge is primarily due to the limited diffusion of electrolyte ions, induced by the polarized rGO/CA/PVDF composite separator endowed with improved piezoelectric characteristics. This work highlights the potential of piezoelectric separators as an effective strategy for long-term energy retention, and offers new insights into the rational design of functional separators with self-discharge mitigation capabilities.