π‐Conjugation Engineering Induced Polyimide Cathode with Electrostatic Confinement for Ultra‐Stable Zinc‐Iodine Batteries

ABSTRACT The practical deployment of aqueous zinc–iodine batteries (ZIBs) is hindered by the polyiodide shuttle effect and the intrinsically sluggish charge transfer within conventional host materials. To address these challenges, we designed a dual‐engineered polyimide cathode through a rational “backbone–side chain” strategy. Specifically, π‐conjugation engineering of the backbone established a carbonyl‐bridged polyimide (BTPI) constructed from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride, which uniquely combined strong chemisorption (binding energy: −2.54 eV) with a narrow bandgap (1.43 eV) arising from enhanced π‐orbital delocalization, thereby enabling enhanced charge‐transfer capability. Building on this optimized conjugated host, side‐chain engineering was employed to obtain quaternary ammonium‐functionalized BTPI (QA‐BTPI), providing potent electrostatic confinement. This synergistic dual‐anchoring network significantly enhanced the overall polyiodide binding energy to −4.47 eV. Consequently, the QA‐BTPI cathode achieved a high reversible capacity (150.6 mAh g −1 at 1 C) and exceptional cycling stability, retaining 92.8% capacity after 10000 cycles at 20 C. This work demonstrates a new design paradigm for energy storage materials via the concerted optimization of π‐conjugation‐regulated charge transfer and multi‐mode confinement.