Closed-Loop Iodine-Oxygen Electrochemistry for High-Reversibility Neutral Zinc–Air Hybrid Batteries

Neutral Zn–air batteries offer advantages in dendrite suppression and carbonation resistance, however, their performance is limited by high overpotentials resulting from insulating discharge products and sluggish oxygen kinetics. Herein, a closed-loop iodide-oxygen cycle mechanism for a neutral aqueous Zn–air/iodide hybrid battery (ZAIB), integrating oxygen and iodide redox chemistry, is proposed. A multifunctional electrocatalyst, featuring FeN nanoparticles anchored on a hierarchically porous carbon matrix, is designed to drives oxygen reduction reactions (ORR) and iodide oxidation/reduction reactions (IOR/IRR). This catalyst spatially confines zinc hydroxyacetate dihydrate (ZHA) precipitates within its honeycomb meso-macroporous framework, thereby preserving triple-phase boundaries. During discharge, I – generated from I 3 – reduction enhances the kinetics, thereby increasing discharge voltage. Concurrently, OH – formed during ORR reacts with the electrolyte to produce ZHA. Upon charging, thermodynamically favored low-potential IOR dominates, regenerating I 3 – from I – and decomposing ZHA to release OH – . The released OH – then spontaneously reacts with I 3 – to regenerate I – and evolve O 2 , resulting in a reduced charge voltage. Consequently, the neutral ZAIB achieves a low charge/discharge voltage gap (640.1 mV), high energy efficiency (54.0%), and exceptional stability (>1800 h at 2 mA cm −2 ). This synergistic mediator-catalyst codesign strategy offers a viable pathway to high-performance neutral metal–air systems.