π-d conjugated coordination mediated catalysis for four-electron-transfer fast-charging aqueous zinc-iodine batteries

Abstract

π-d conjugated coordination polymers (CCPs) with unique stacking structures are developed for the nanoconfinement of iodine by chemisorption in an aqueous Zn-I₂ battery. The stacking structure allows for the accumulation of localized electrons on a well-ordered atomic array, which enhances the built-in electric field, thereby optimizing the environment for the evolution of iodine species. The assembled I⁻/I⁰ two-electron-transfer Zn-I₂ battery provides a specific capacity of 226.4 mAh g⁻¹ at 0.4 A g⁻¹ (an overpotential of 42 mV) and achieves 60,000 cycles at 10 A g⁻¹. The assembled I⁻/I⁰/I⁺ four-electron-transfer Zn-I₂ battery provides a specific capacity of up to 337.1 mAh g⁻¹ at 5 A g⁻¹ with outstanding rate performance (155.6 mAh g⁻¹ at 50 A g⁻¹) and cycle performance (12,000 cycles at 10 A g⁻¹). This study employs targeted molecular design and systematic optimization to develop a high-performance aqueous Zn-I₂ battery electrode material enabled with the promising four-electron transfer reaction.