Ionic liquid-induced dynamic interfacial ion buffer zones for wide-temperature and stable zinc-iodine batteries.

Aqueous zinc-iodine batteries (Zn‖I2) are promising for large-scale energy storage. However, their practical deployment is severely hindered by parasitic reactions at the zinc anode, uncontrolled polyiodide shuttling, and sluggish interfacial ion-transfer kinetics, especially under a wide temperature range. Herein, we propose an ionic liquid (IL)-induced interfacial ion buffer zone strategy that fundamentally reconstructs the electrolyte-electrode interphase chemistry. The introduced IL molecules participate in the Zn2+ solvation sheath and dynamically reorganize the local coordination environment, forming a Zn2+ buffer layer at the anode interface and an iodine species buffer region at the cathode side. This dual-buffer configuration enables decoupled regulation of ion desolvation and interfacial transport. The IL-derived anion-rich interphase homogenizes the electric field and regulates the Zn2+ flux, thereby suppressing dendritic growth and parasitic side reactions. Meanwhile, the IL mediates the reversible conversion of polyiodide species through confined coordination interactions, effectively mitigating shuttle effects and active material loss. More importantly, the IL-derived electrolyte exhibits temperature-adaptive solvation behavior, weakening the hydrogen-bonding network of water and lowering the desolvation energy barrier of Zn2+, which ensures fast ion-transfer kinetics across a wide temperature range (-40 to 60 °C). As a result, the optimized electrolyte enables highly reversible Zn plating/stripping and efficient iodine redox conversion. Zn‖Zn symmetric cells sustain stable cycling for over 5000 h at 1 mA cm-2/0.5 mAh cm-2. Moreover, Zn‖I2 full cells exhibit ultralong cycling stability over 50 000 cycles at 10 A g-1. This work provides a new paradigm for electrolyte interfacial ion regulation in aqueous battery systems.