An Artificial Interphase of Ionic Liquid (EMIMTFSI) for High Performance Aqueous Zn-I₂ Batteries

Aqueous Zn-I₂ 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-I₂ 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 H₂O and suppresses parasitic reactions. Moreover, EMIM⁺ hinders iodine dissolution and forms an EMIM⁺-I₃ ^- 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-I₂ 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-I₂ batteries that effectively addresses the challenges of dendrite formation and the shuttle effect.