Synergistic effects of Lewis acid–base and Coulombic interactions for high-performance Zn–I2 batteries

Zinc–iodine batteries are considered promising energy storage devices due to the presence of non-flammable aqueous electrolytes and intrinsically safe zinc. However, the polyiodide shuttle effect and sluggish reaction kinetics limit their electrochemical performance. Herein, in this work, we synthesized a high-performance host material—the iodine covalent post-functionalized zeolitic imidazolate framework-90 (IL-ZIF-90) with multifunctional nitrogen—to achieve intense adsorption of iodine species. The positively charged nitrogen (N+) can induce Coulombic interactions with negatively charged iodine, while the nitrogen with a lone pair of electrons (Nle) serving as a Lewis base can interact with I2 which acts as a Lewis acid. Density functional theory (DFT) calculations are in accordance with the electrochemical characterization studies, indicating that the Nle species can accelerate the conversion between I2 and I−. Consequently, the cathode enables a capacity of 120.3 mA h g−1 at 4 A g−1, and exhibits an excellent rate capability with a capacity of 86.8 mA h g−1 at a high current density of 20 A g−1. Furthermore, the cathode also demonstrates excellent cyclic stability with a capacity retention of 91.7% at 10 A g−1 after 65 000 cycles. This work provides an effective strategy to realize high-performance Zn–I2 batteries and can be extended to other metal–iodine battery technologies.