Molecularly engineered three-dimensional covalent organic framework protection films for highly stable zinc anodes in aqueous electrolyte

Metallic Zn has been regarded as ideal anodes in aqueous electrolyte owing to its high theoretical capacity, intrinsic safety, low cost, and nontoxicity. However, the Zn dendrite growth and the side-reactions hindered the practical application of Zn anode. Herein, a thin and uniform three-dimensional (3D) COOH-functionalized covalent organic frameworks (COF) film (denoted as 3D-COOH-COF) is designed and in-situ synthesized as a protective layer to stabilize the Zn anode. The thin 3D-COOH-COF protection film with abundant negative functional groups and homogeneous nanochannels facilitates the fast transport of Zn2+, impedes the pass through of SO42−, and significantly suppresses the corrosion reactions, leading to an excellent electrochemical performance. The novel 3D-COOH-COF protective film enables the Zn||Zn symmetric cells to stably cycle for over 2000 h at 1 mA cm−2 and an average Coulombic efficiency of Zn plating/stripping as high as 99.5% for 1000 cycles at 1 mA cm−2.This finding provides a facile and promising route to regulate the deposition behavior of Zn in aqueous electrolyte.