Halogen Bonding-Sustained Accumulation of Polyiodide in Hierarchically Open Micellar Film for Shuttle-Free...

Polyiodides shuttling normally leads to low coulombic efficiency and rapid capacity fading under extended charging-discharging durations, thereby limiting the application of Zn-I₂ 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@I₂ 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-I₂ 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.