Multiscale Confinement Electrolyte Enables Low‐Temperature Stable Aqueous Zinc‐Iodine Batteries

ABSTRACT Aqueous zinc‐iodine batteries are promising candidates for safe and low‐cost energy storage but suffer from severe degradation under low‐temperature and high‐rate conditions due to electrolyte freezing, iodine dissolution, sluggish ion transport, and interfacial instability. Herein, we report a multiscale confinement electrolyte by introducing high‐concentration Ca(ClO 4 ) 2 and a small amount of starch into a Zn(OTf) 2 system to regulate solvation structure, iodine chemistry, and electrode interfaces simultaneously. The strong hydration capability of Ca 2+ reconstructs the hydrogen‐bond network, reduces water activity, suppresses ice crystallization, and preserves ion transport at subzero temperatures. Meanwhile, Ca 2+ confines iodide and polyiodide species through strong electrostatic interactions, thereby suppressing I 2 dissolution, inhibiting shuttle effects, and mitigating active material loss. Starch further constructs an interfacial confinement layer on the Zn anode, inhibiting parasitic reactions, reducing by‐product formation, and guiding uniform Zn deposition. Benefiting from these synergistic effects, Zn||I 2 batteries deliver an exceptional rate capability of 15 A g −1 and achieve ultrastable cycling over 60 000 cycles at this ultrahigh rate. Moreover, the batteries operate reliably at –40°C, delivering over 3600 h of cycling at 0.5 A g −1 with 95.8% capacity retention. High‐loading pouch cells and a preliminary 1.1 Ah‐level demonstration further confirm the practical scale‐up potential of this electrolyte strategy.