Efficient I^-/I₃ ^-/I₂ Conversion and Shuttle-Suppression in High-Rate Ah-Level Zinc-Iodine Batteries Enabled by...

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).