Dual‐Zone Chloride Engineering to Enable Ultra‐Stable Two‐Electron Zinc‐Iodine Batteries
Leiqian Zhang, Jiaming Gong, Hele Guo, Jiajia Huang, Suli Chen, Jean‐François Gohy, Yazhou Zhou, Johan Hofkens, Tianxi Liu, Kläus Müllen, Feili Lai
Abstract
Abstract Zinc‐iodine batteries (ZIBs) with organic iodine hosts that harness the I − /I + conversion offer a promising route to high‐energy storage but remain limited by rapid capacity decay. Conventional approaches employing high‐concentration ZnCl 2 electrolytes effectively activate I − /I + conversion in carbon hosts but prove incompatible with organic systems. Here, its excess free Cl − is identified to displace polyiodide from organic iodine hosts, thereby triggering an irreversible I − /I + process. To address this, a dual‐zone chloride engineering strategy is introduced that spatially separates chloride environments into complementary domains. At the cathode, a non‐dissociative hydrophobic salt (trioctylmethylammonium chloride) establishes a confined Cl − ‐rich, water‐deficient environment, suppressing polyiodide desorption and preventing hydrolytic I⁺ decomposition. In the electrolyte, a chloride‐liberating salt (0.2 m ZnCl 2 ) dissolved in a glycerol‐water solvent replenishes free Cl − to fully activate I 0 /I⁺ conversion while enhancing high‐voltage tolerance. This cooperative design delivers an organic‐based two‐electron ZIB with 87.0% capacity retention over 11,000 cycles, and validates its universality in a carbon‐based ZIB retaining 87.2% capacity after 35,000 cycles. By uniting cathodic confinement with electrolyte liberation, dual‐zone chloride engineering establishes a generalizable framework for stabilizing two‐electron iodine redox chemistry, paving the way toward durable, high‐energy aqueous ZIBs.