"Zn-Iodine" Co-Regulation Induced by Trifunctional Zn-Exchanged Electrolyte Additives for High-Areal-Capacity and Robust Zn-I Batteries.

Aqueous Zn-I batteries featuring high safety and low cost attract considerable attention for grid-scale energy storage. However, the challenges of Zn dendrite growth, hydrogen evolution reaction, and polyiodide shuttling severely impede their practical application. This study introduces Zn-exchanged vermiculite nanosheets (ZVN) as a multifunctional electrolyte additive to optimize Zn solvation structure, facilitating hydrated Zn ion de-solvation via the strong electron affinity of ZVN. Moreover, the in situ formed protective ZVN layer on Zn anode maintains superior ionic conductivity for Zn transportation, enabling highly stable and dendrite-free Zn deposition. This dual mechanism enables a dendrite-free Zn anode with 99.82% Coulombic efficiency over 1 700 cycles in Zn//Cu cells. Simultaneously, the excellent iodine species trapping ability of ZVN effectively inhibits the polyiodide shuttling for improved iodine conversion efficiency. Therefore, the assembled Zn-I battery based on polyaniline/I cathode exhibits a high areal capacity of 1.05 mAh cm and ultra-long lifespan over 18 000 cycles. This study provides an efficient electrolyte additive with a "Zn-iodine" synergistic effect for advanced Zn-I batteries.