Halogen Bonding‐Sustained Accumulation of Polyiodide in Hierarchically Open Micellar Film for Shuttle‐Free Long‐Duration Zn‐I 2 Battery

ABSTRACT Polyiodides shuttling normally leads to low coulombic efficiency and rapid capacity fading under extended charging‐discharging durations, thereby limiting the application of Zn‐I 2 batteries in long‐duration energy storage (LDES). In this study, self‐assembled film of polystyrene‐ b ‐poly(2‐vinylpyridine) (PS‐ b ‐P2VP) spherical micelles on activated carbon (AC) is employed as a host for iodine species. The PS‐ b ‐P2VP micellar film provides abundant spatially distributed pyridyl groups for massive accumulation of iodine through halogen bonding. Moreover, compared to the dense film of P2VP homopolymer, the brush‐like P2VP corona within the PS‐ b ‐P2VP micellar film creates a hierarchically open platform that facilitate the deep diffusion and robust encapsulation of iodine species. Such distinct structural feature remarkably suppresses the shuttling effect of polyiodides in prolonged charging‐discharging duration. Thus, the resulting AC/PS‐ b ‐P2VP@I 2 cathode reveals high coulombic efficiency of 97.3% and high capacity of 191.6 mAh g −1 under a long charging‐discharging duration exceeding 20 h, maintaining 96.8% capacity over 2000 h (100 cycles). Furthermore, the assembled Zn‐I 2 pouch cell demonstrates exceptional performance by powering an LED display screen for over 9.7 h, following a 24‐h rest after fully charged, highlighting its promising potential for LDES applications.