A Symmetric Aqueous Magnesium Ion Supercapattery Based on Covalent Organic Frameworks

by Guodong Zou, Zhengnan Tian, Vinayak S. Kale, Wenxi Wang, Sharath Kandembeth, Zhen Cao, Jing Guo, Justyna Czaban-Jóźwiak, Luigi Cavallo, Osama Shekhah, Mohamed Eddaoudi, Husam N. Alshareef
Year: 2022 DOI: https://doi.org/10.1002/aenm.202203193


Aqueous magnesium ion-based batteries have attracted significant research interest due to the two-electron transfer process, small cation radius, low reduction potential as well as the inert hydrogen evolution reaction. However, the high surface charge density of divalent Mg2+ ions results in sluggish solid-state diffusion kinetics, which significantly limits the number of host materials suitable for effective Mg2+ ion storage. Here, for the first time, covalent organic frameworks (COFs) are explored as host materials for high-rate aqueous Mg2+ ion batteries. Combining electrochemical and spectral characterization with theoretical simulation, a synergistic charge storage mechanism involving the reaction of nitrogen and oxygen bridged by Mg2+ ions is revealed. Using electrochemical analysis, it is shown that the Mg2+ ion diffusion kinetics are dominated by the surface pseudocapacitive behavior in COFs, which achieves a favorable rate performance and durable cyclic stability. This work offers a new perspective on the storage of Mg2+ ions in COF host materials.