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

The\ndetrimental Zn dendrites and side reactions occurring at Zn/electrolyte\ninterfaces severely reduce the cycling stabilities of Zn anodes and\nretard the large-scale deployment of Zn-based aqueous energy storage\nsystems. In this study, an electro-spun polyacrylonitrile/polyvinylidene\nfluoride composite electro-spun fiber (PAN/PVDF, PF) membrane with\na high porosity and a uniform pore-size distribution was employed\nas an ion divider layer to optimize the interfacial Zn<sup>2+</sup> migration behavior and the Zn deposition environment. This membrane\nis rich in electronegative polar groups that coordinate strongly with\nZn<sup>2+</sup>, accelerate its desolvation, and promote its interfacial\nmigration. The PF ion divider layer possesses a high ionic conductivity\nand Zn<sup>2+</sup> transference number. The PF membrane exhibits\nexcellent Zn<sup>2+</sup> absorption characteristics owing to its\nfunctional groups and uniform pores, acting as an ion sieve to achieve\nuniform Zn<sup>2+</sup> distribution. The prepared Zn//Zn symmetric\ncell exhibited cycle lives >1350 and 3000 h in 2 M Zn­(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> and ZnSO<sub>4</sub> electrolytes at\n5 mA cm<sup>–2</sup>, respectively. The Zn//active carbon capacitor\nmaintained a capacity retention of 78.6% after 35,000 cycles at 2\nA g<sup>–1</sup> and a good performance at 55 °C under\n180° folding. This study provides new insights for constructing\nflexible and foldable Zn-based energy storage systems.