Coordination competition and hydrogen-bond reconstruction enable reversible I⁺/I₂/I^- conversion for large-capacity...

Four-electron aqueous zinc-iodine batteries (4eZIBs) offer high energy density but suffer from irreversible I⁺ hydrolysis, polyiodide shuttling, poor zinc anode stability, and a limited operating temperature range. Here, we propose a coordination competition and hydrogen-bond reconstruction strategy using a hybrid electrolyte of Zn(ClO₄)₂·6H₂O, ZnCl₂, InCl₃, and polyethylene glycol 400 (PEG400), which enables reversible I⁺/I₂/I^- conversion for large-capacity Zn‖I₂ batteries over a wide temperature range. Specifically, In³⁺ ions suppress polyiodide formation through preferential coordination with I^- and electrostatic shielding that blocks charge exchange between I^- and I₂, and they are also preferentially reduced to metallic indium on the zinc anode surface, forming a protective indium layer that inhibits hydrogen evolution and corrosion. Meanwhile, PEG400 reduces the activity of free water by reconstructing the hydrogen-bond network of water molecules, and its polar segments can confine the ICl intermediate to suppress I⁺ hydrolysis. This synergistic chemistry enables an ultra-long Zn anode lifespan (over 4000 h), excellent Zn‖I₂ full cell stability (over 10 000 cycles), record wide-temperature operation (-50 °C to 70 °C), and scalable Ah-level pouch-cell stability. This work provides a robust strategy for simultaneously managing complex interhalogen chemistries and stabilizing the zinc anode, paving the way toward practical aqueous energy storage.