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

Abstract

Zn-based aqueous batteries have attracted much attention because of their high theoretical-capacity, safety, and low-cost, yet the H₂-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 H₂-evolution and Zn²⁺ flux. Best of them, Zn-AAn-COF based cell only produces 0.002 mmol h⁻¹ cm⁻² H₂, 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 H₂-evolution and homogenize the ion-distribution or electric-filed to achieve high performance.