Tailoring zinc diatomic bidirectional catalysts achieving orbital coupling–hybridization for ultralong-cycling zinc–iodine batteries†

Abstract

Aqueous zinc–iodine (Zn–I₂) batteries have become promising energy storage devices due to their high theoretical capacity, high safety, and low cost advantages. However, sluggish kinetics and the shuttle effect of polyiodides still limit the further development of Zn–I₂ batteries. Single-atom catalysts have been explored in Zn–I₂ batteries to address the above challenges, but single atom sites restrict the adsorption/desorption relationship of reactants and intermediates. Herein, honeycomb shaped Zn dual atom sites embedded in nitrogen doped carbon nanosheets were designed to not only enhance the confinement of I₂, but also facilitate the bidirectional redox kinetics of polyiodides through orbital coupling and hybridization, thereby improving the capacity and cycle stability of Zn–I₂ batteries. Impressively, the batteries with I₂@Zn₂NC cathodes received the longest cycle of 100 000 cycles at 50C, retaining an ultra-low capacity fading of 0.0002% per cycle. Additionally, the batteries achieved 7000 cycles at 10C even at −20 °C, verifying good catalytic performance of Zn₂NC at low temperature. This work reveals the mechanism of synergistic adsorption and catalytic conversion of polyiodides by dual single atom catalysts, providing guidance for the design of dual atom site structures to achieve state-of-the-art Zn–I₂ batteries.