Efficient I-/I3 -/I2 Conversion and Shuttle-Suppression in High-Rate Ah-Level Zinc-Iodine Batteries Enabled by Bifunctional Confined-Catalyst ZrB2/AC Host.

Rechargeable aqueous Zn||I2 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 (I3 - and I5 -) seriously affect the rate capability and cycling stability of Zn||I2 battery. Herein, ZrB2 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 I3 - and further to I2 during charging, thereby reducing the energy barrier and improving iodine utilization. Consequently, the Zn||I2@ZrB2/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||I2@ZrB2/AC pouch cell with a high I2 mass loading of 33 mg cm-2 maintains a stable capacity of 1.2 Ah over 600 cycles (more than 1400 h).