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 (N-le) serving as a Lewis base can interact with I-2 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 I-2 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-I-2 batteries and can be extended to other metal-iodine battery technologies.

Automated summary

In order to improve the performance of zinc-iodine batteries, researchers synthesized a high-performance host material that utilizes nitrogen atoms to enhance the electrochemical performance of the battery. The experimental results show that the material exhibits excellent capacity, rate capability, and cyclic stability.