Chelation-Driven Dual-Interface Regulation for Long-Life Aqueous Zn-I2 Batteries.

The growing demand for energy storage systems (ESS) driven by the expansion of renewable energy calls for aqueous Zn-I2 batteries that offer both safety and cost competitiveness. However, the hydrogen evolution reaction (HER) and Zn anode corrosion, combined with iodine dissolution and polyiodide shuttling at the I2 cathode, form a degradation loop through interelectrode interactions, that impairs battery lifespan and efficiency. This study proposes a dual-interface regulation strategy by introducing the multidentate chelator TPEN as an electrolyte additive. This strategy promotes the formation of Zn2+-TPEN coordination species (TCC) in the electrolyte, which reconfigures the electric double layer of Zn anode into an interfacial environment with reduced water accessibility via interfacial adsorption, suppressing HER and corrosion, and stabilizing local pH fluctuations while promoting uniform nucleation and deposition. Simultaneously, at the I2 cathode, it traps polyiodide to reduce free polyiodide concentration and directs the reaction pathway toward the interface, thereby decreasing shuttling and self-discharge while improving I2 deposition uniformity. As a result, the Zn||Zn symmetric cell operated stably for over 2000 h and achieved a Coulombic efficiency of over 96.2% and a capacity retention of 92.5% after 200 cycles under high-loading I2 (5.5 mAh cm-2) and 0.18 C conditions.