Crystalline Lithium Imidazolate Covalent Organic Frameworks with High Li-Ion Conductivity

• Published in: Journal of the American Chemical Society 2019-05, Vol.141 (18), p.7518-7525
• Main Authors: Hu, Yiming, Dunlap, Nathan, Wan, Shun, Lu, Shuanglong, Huang, Shaofeng, Sellinger, Isaac, Ortiz, Michael, Jin, Yinghua, Lee, Se-hee, Zhang, Wei
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.9b02448

Ionic covalent organic frameworks (ICOFs) have recently emerged as promising candidates for solid-state electrolytes. Herein, we report the first example of a series of crystalline imidazolate-containing ICOFs as single-ion conducting COF solid electrolyte materials, where lithium cations freely travel through the intrinsic channels with outstanding ion conductivity (up to 7.2 × 10–3 S cm–1) and impressively low activation energy (as low as 0.10 eV). These properties are attributed to the weak Li ion–imidazolate binding interactions and well-defined porous 2D framework structures of such ICOFs. We also investigated the structure–property relationship by varying the electronic properties of substituents (electron donating/withdrawing) that covalently attached to the imidazolate groups. We found electron-withdrawing substituents significantly improve the ion-conducting ability of imidazolate-ICOF by weakening ion-pair interactions. Our study provides a convenient bottom-up approach toward a novel class of highly efficient single-ion conducting ICOFs which could be used in all solid-state electrolytic devices.