Efficient I ⁻ /I ₃ ⁻ /I ₂ Conversion and Shuttle‐Suppression in High‐Rate Ah‐Level Zinc‐Iodine Batteries Enabled by Bifunctional Confined‐Catalyst ZrB ₂ /AC Host

Abstract

ABSTRACT Rechargeable aqueous Zn||I 2 batteries have received significant attention for the high energy density, inherent safety, and ecological friendliness. However, the sluggish iodine redox kinetics and the formation of highly soluble polyiodide (I 3 − and I 5 − ) seriously affect the rate capability and cycling stability of Zn||I 2 battery. Herein, ZrB 2 is synthesized as a catalyst host for polyiodide conversion, where unsaturated surface Zr atoms provide Lewis‐acid sites that enable strong interaction with polyiodide species. These sites not only confine polyiodide anions through strong adsorption to suppress polyiodide shuttling, but also catalyze their stepwise conversion from I − to I 3 − and further to I 2 during charging, thereby reducing the energy barrier and improving iodine utilization. Consequently, the Zn||I 2 @ZrB 2 /AC full cell displays remarkable rate performance, retaining 80.5% of the capacity as the current density increases from 1 to 10 A g −1 . Remarkably, the full cells exhibit exceptionally long cycle life of 50,000 cycles with negligible capacity decay. The Zn||I 2 @ZrB 2 /AC pouch cell with a high I 2 mass loading of 33 mg cm −2 maintains a stable capacity of 1.2 Ah over 600 cycles (more than 1400 h).