Hofmeister‐Regulated Amide‐Protonated Hydrogel Enables Organo‐Interhalogen Conversion‐Type Quasi‐Solid‐State Zn Batteries With Practical Iodine Loadings

ABSTRACT Organo‐interhalogen‐mediated four‐electron iodine conversion (I − /I 0 /I + ) promises high‐energy Zn batteries (4eZIBs) in noncorrosive aqueous electrolytes. Yet, polyiodide shuttling and I + hydrolysis restrict shorten cycle life at high iodine loadings. Here we report a dual‐anionic Hofmeister‐regulated amide‐protonated polyacrylamide (pPAM) hydrogel electrolyte to solve this issue. Consistent with experimental observations, underlying mechanistic interpretations are proposed. The potential protonated site ─COHNH 2 + in pPAM can interact with iodine species (I 3 − , I 2 , and organo‐interhalogen adduct), effectively suppressing active material loss during cycling. The dual‐anion‐regulated Hofmeister effect may contribute to control molecular mediator (2‐bromoacetamide, BrAce) flux within the pPAM gel, enabling fast organo‐interhalogen conversion. The extensive hydrogen‐bonding network of the hydrogel reshapes the hydrogen‐bonding environment of water, suppressing organo‐interhalogen adduct (I + species) hydrolysis. The resulting quasi‐solid‐state 4eZIBs substantially outperform aqueous counterparts and state‐of‐the‐art results. At 15.6 mg cm −2 iodine loading, stable cycling exceeds 2000 cycles at 15 mA cm −2 . At 28.3 mg cm −2 , the battery delivers an areal capacity of 9.95 mAh cm −2 and an areal energy density of 10.85 mWh cm −2 . An Ah‐level pouch cell cycles 50 times at 0.5 mA cm −2 , with an energy density of 305.27 Wh kg iodine −1 . This work provides a hydrogel design principle for organo‐interhalogen‐mediated conversion, advancing practical high‐loading 4eZIBs and beyond.