Functional Cellulose Acetate/ PVDF Binary Piezoelectric Membranes Toward Reducing Self‐Discharge in Solid‐State Supercapacitors

ABSTRACT Supercapacitors are high‐power‐density energy storage devices essential for applications requiring rapid energy delivery. However, their practical implementation is often hindered by significant self‐discharge. Functional separators capable of regulating ion transport offer an effective strategy to mitigate self‐discharge without compromising electrochemical performance. In this work, a functional binary piezoelectric membrane based on cellulose acetate (CA) and poly(vinylidene fluoride) (PVDF) is fabricated via electrospinning and employed as a high‐performance separator. The electrospun PVDF matrix provides intrinsic piezoelectricity, enabling the modulation of ion flux via a built‐in electric field. Meanwhile the incorporation of CA significantly enhances electrolyte affinity, liquid uptake, and mechanical integrity. Benefiting from high porosity, and strong polarity, the separator delivers outstanding electrochemical performance in solid‐state supercapacitors, achieving a high specific capacitance of 194.5 F g −1 at 0.5 A g −1 with over 10,000 stable cycles. Crucially, the functional separator effectively suppresses the self‐discharge rate to ~18.7 mV h −1 and retains 44% of the initial voltage after 24 h, which is an approximately 28% improvement in charge retention over the commercial separator. This work demonstrates that electrospun piezoelectric CA/PVDF composite membranes are promising functional separators for next‐generation supercapacitors with low self‐discharge.