An Artificial Interphase of Ionic Liquid (EMIMTFSI) for High Performance Aqueous Zn‐I 2 Batteries

ABSTRACT Aqueous Zn‐I 2 batteries suffer from short cycle life due to zinc (Zn) dendrite growth and polyiodide shuttle‐induced corrosion. To address these key challenges, a multifunctional protective film of 1‐ethyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI) ionic liquid, denoted as IL@Zn, was constructed on the Zn anode surface via a tape‐casting method to improve the cycle life of Zn‐I 2 batteries. EMIM + cations preferentially adsorb on Zn, creating a water‐lean inner Helmholtz plane (IHP) and providing steric hindrance for uniform Zn nucleation, while hydrophobic TFSI − anions enrich at the surface to build a water‐repellent interface that excludes H 2 O and suppresses parasitic reactions. Moreover, EMIM + hinders iodine dissolution and forms an EMIM + ‐I 3 − dominant phase, mitigating the polyiodide shuttle and the associated Zn corrosion. Consequently, IL@Zn symmetric cells deliver over 350 h of stable cycling at 5.0 mA cm −2 . Zn‐I 2 full cells with IL@Zn anodes retain 82% capacity after 2000 cycles at 2 A g −1 and exhibit higher Coulombic efficiency (CE) after self‐discharge than cells with unprotected Zn anodes. This work demonstrates a facile strategy for aqueous Zn‐I 2 batteries that effectively addresses the challenges of dendrite formation and the shuttle effect.