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

Abstract

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 (N_le) 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 N_le 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.