Strategic Nitrogen Site Alignment in Covalent Organic Frameworks for Enhanced Performance in Aqueous Zinc-Iodide
Liying Yin1,2, Xiaoyu Guo1, Junfang Hu1
1Key Laboratory of Polyoxometalate and Reticular Material Chemistry of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, China.
Abstract:
Aqueous zinc-iodine batteries (AZIBs) are gaining attention as next-generation energy storage systems due to their high theoretical capacity, enhanced safety, and cost-effectiveness. However, their practical application is hindered by challenges such as slow reaction kinetics and the persistent polyiodide shuttle effect. To address these limitations, we developed a novel class of covalent organic frameworks (COFs) featuring electron-rich nitrogen sites with varied density and distribution (N1-N4) along the pore walls. These nitrogen sites enhance iodine species confinement and mass transport. Our experimental and theoretical studies reveal that the continuous and optimized distribution of nitrogen sites within the COF structure significantly reduces internal resistance and boosts redox activity. Moreover, the N4-COF demonstrates superior performance compared to other porous materials, due to its high density and strategic alignment of active sites. The I2@N4-COF cathode achieves a remarkable specific capacity of 348 mAh g-1 at 1 C, almost 1.8 times greater than that of the I2@N1-COF, while also maintaining excellent cycling stability. This integration of a porous framework with aligned nitrogen sites in the N4-COF structure not only enhances iodine redox behavior but also offers a promising design strategy for developing high-performance AZIB electrodes.
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