Synergistic\nConstruction of Hierarchical Tree-Ring\nStructures and Blocked Interfaces for Stable, Flexible Zinc–Iodine\nBatteries with Ultrahigh Areal/Gravimetric Capacity

The development of aqueous zinc–iodine (Zn–I<sub>2</sub>) batteries is plagued by long-term cycling stability, mainly\ncaused by limited iodine loading, polyiodide shuttle, and uneven Zn<sup>2+</sup> deposition. Herein, a unique tree-ring-like hierarchical\nstructure constructed by polyaniline (PANI) nanofiber arrays and reduced\ngraphene oxide (RGO) was designed to provide the nanopore array for\nprestoring iodine ions and confine the iodine conversion reaction\nas well as promote electron and ion transport along PANI nanofibers,\nthereby enhancing the capacity and cycling durability of Zn–I<sub>2</sub> batteries. Meanwhile, the sulfonic polyacrylamide/glycerol\n(SPAM/Gly) hydrogel electrolyte containing the ZnI<sub>2</sub> additive\nis introduced for simultaneously inhibiting the polyiodide shuttle\nand side reactions on the Zn anode accompanied by excellent antifreezing\nproperties and flexibility. As a result, the assembled flexible battery\nrealized a remarkable areal capacity of 2.3 mAh·cm<sup>–2</sup> at 0.5 mA·cm<sup>–2</sup> (corresponding to 287.5 mAh·g<sup>–1</sup>) and a maximum energy density of 2.54 mWh·cm<sup>–2</sup> at a high mass loading of 8 mg·cm<sup>–2</sup>. Consequently, the battery still exhibited a capacity of 0.784 mAh·cm<sup>–2</sup> over 6000 cycles and 0.98 mAh·cm<sup>–2</sup> after 200 cycles under −20 °C at 2 mA·cm<sup>–2</sup>. Such flexible device also maintains a steady supply of powering\nelectronic gadget during deformations.