Alkyne−Functionalized Covalent Organic Frameworks for Suppressing Polyiodide Shuttle Effect in Aqueous Zinc−Iodine Batteries

Aqueous zinc−iodine (Zn−I2) batteries demonstrate promising potential for large−scale energy storage applications. However, the uncontrolled “shuttle effect” of polyiodides (I3−, I5−) results in capacity loss, lower Coulombic efficiency (CE), and poor cycling reversibility. Herein, we propose alkyne−rich covalent organic frameworks (COFs) as functional separator coatings to effectively suppress the “shuttle effect”, establishing a protective solid electrolyte interphase (SEI) layer to stabilize the Zn metal anode. The effect of different alkyne contents in COFs on the performance of Zn−I2 batteries is investigated, and the results demonstrate that increasing alkyne content significantly improves CE, ion migration rate, and cycling stability. Remarkably, the 100% alkyne−functionalized TAPT−BPTA−COF separator exhibited excellent ion selectivity, effectively blocking the diffusion of polyiodide species, while favoring the transport of Zn2+. This selective transport ensures uniform deposition of Zn2+ on the anode during cycles, thereby reducing internal resistance and improving cycle performance. Notably, the Zn||TAPT−BPTA−COF||I2 battery delivers an initial capacity of 8.4 mAh cm−2 at 20 mA cm−2, retaining 70.1% of the initial capacity over 1200 cycles with 99% CE. Complementary spectroscopic analyses and visualization experiments further confirm that the fully alkyne−conjugated electronic structure of COFs enhances electrical conductivity. This study provides a molecular design strategy for developing high−performance, COF−based electrochemical materials for Zn−I2 battery systems.