Synergistic Manipulation of Hydrogen Evolution and Zinc Ion Flux in Metal-Covalent Organic Frameworks for Dendrite-free Zn-based Aqueous Batteries.

Zn-based aqueous batteries have attracted much attention because of their high theoretical-capacity, safety, and low-cost, yet the H 2 -evolution, qualification or inhibition mechanism investigations that are closely related to the dendrite-growth are rare and challenging. Herein, a series of zincophilic metal-covalent organic frameworks (e.g., Zn-AAn-COF, Zn-DAAQ-COF, and Zn-DAA-COF) have been explored as model-platforms to manipulate the H 2 -evolution and Zn 2+ flux. Best of them, Zn-AAn-COF based cell only produces 0.002 mmol h -1  cm -2  H 2 , which is >2 orders of magnitude lower than bare Zn. Noteworthy, it affords high stability for 3000 cycles (overpotential, <79.1 mV) at 20 mA cm -2 in symmetric-cell and enhanced cycling-stability up to 6000 cycles at 2000 mA g -1 in the assembled full-battery. Besides, mechanistic characterizations show that Zn-AAn-COF can enhance the energy-barrier of H 2 -evolution and homogenize the ion-distribution or electric-filed to achieve high performance.