Combining Inner Helmholtz Plane Adjustment and Gibbs–Thomson Effect to Enable Ultra‐High Utilization of Zinc Electrodes and Inhibit Polyiodide Shuttling

Abstract Aqueous zinc‐based batteries represent a promising energy storage technology due to their cost‐effectiveness, high reliability, and large power output. However, their widespread application is hindered by dendrite formation and hydrogen evolution, both stemming from the Zn metal electrode. To overcome these limitations, this study introduces an anionic surfactant with a long (CH ₂ CH ₂ O) ₉ chain as an electrolyte additive for zinc‐iodine batteries. The proposed additive functions through multiple synergistic mechanisms. It preferentially adsorbs onto the surface of Zn electrode to modify the inner Helmholtz plane (IHP) for creating a water‐poor environment through its large‐sized hydrophobic chain, hence effectively suppressing water‐induced parasitic reactions. Its carboxylate group and (CH ₂ CH ₂ O) ₉ chain guide Zn ²⁺ ion flux for uniform deposition. By reducing electrolyte surface tension, it promotes finer grain formation through the Gibbs–Thomson effect, further enhancing Zn deposition homogeneity. Additionally, the additive modifies the cathode IHP, effectively mitigating polyiodide shuttle effect. Experimental results demonstrate that the lifespan of Zn//Zn cells can be significantly enhanced even under ultra‐high areal capacities. The zinc‐iodine batteries achieve exceptional stability over 16 000 cycles while maintaining good cyclability under high iodine mass loading (>14 mA cm ⁻² ) and Zn‐deficient configurations. These findings provide novel insights into electrolyte engineering for advanced zinc‐based battery systems.