Highly Crystalline Flower-Like Covalent-Organic Frameworks Enable Highly Stable Zinc Metal Anodes

Aqueous zinc (Zn) ion batteries with low cost and high safety are promising devices for grid energy storage; however, the Zn anode problems, including dendrite growth and parasitic side reactions, severely retard their practical implementation. Here, a two-dimensional covalentorganic framework (COF) coating is developed to address these issues. Under the regulation of an optimal modulator, the prepared COF (COF- H) containing rich alkynyl units in an AA-stacking mode not only features a flower-like structure but also exhibits high crystallinity, large surface area, and high stability in strong acid and base medium. Consequently, the Zn anode with this COF-based artificial interface layer greatly mitigates the surface corrosion and efficiently suppresses the growth of the Zn dendrite, which is mainly attributed to the homogeneous distribution of Zn2+ in uniform channels and strong affinity of electron-rich sites including alkynyl, ketone, and enamine groups in COF-H toward Zn2+. The resulting Zn anode endows the symmetric cell with a long cycling lifetime of over 900 h at 3 mA cm-2 and promotes the cyclability of the COF@ Zn||MnO2 full cell. This study provides insights into designing highly crystalline COFs and constructing a highly reversible Zn anode for advanced rechargeable aqueous Zn ion batteries.