PAN–PVDF Fiber Membrane as a Uniform Ion Divider Layer for Reversible Zinc Anodes and Long-Life Zinc-Ion Capacitors

The detrimental Zn dendrites and side reactions occurring at Zn/electrolyte interfaces severely reduce the cycling stabilities of Zn anodes and retard the large-scale deployment of Zn-based aqueous energy storage systems. In this study, an electro-spun polyacrylonitrile/polyvinylidene fluoride composite electro-spun fiber (PAN/PVDF, PF) membrane with a high porosity and a uniform pore-size distribution was employed as an ion divider layer to optimize the interfacial Zn2+ migration behavior and the Zn deposition environment. This membrane is rich in electronegative polar groups that coordinate strongly with Zn2+, accelerate its desolvation, and promote its interfacial migration. The PF ion divider layer possesses a high ionic conductivity and Zn2+ transference number. The PF membrane exhibits excellent Zn2+ absorption characteristics owing to its functional groups and uniform pores, acting as an ion sieve to achieve uniform Zn2+ distribution. The prepared Zn//Zn symmetric cell exhibited cycle lives >1350 and 3000 h in 2 M Zn(CF3SO3)2 and ZnSO4 electrolytes at 5 mA cm–2, respectively. The Zn//active carbon capacitor maintained a capacity retention of 78.6% after 35,000 cycles at 2 A g–1 and a good performance at 55 °C under 180° folding. This study provides new insights for constructing flexible and foldable Zn-based energy storage systems.