Uniform Longitudinal Zinc Growth beyond Interface Guided by Anionic Covalent Organic Framework for Dendrite-Free Aqueous Zinc Batteries

Abstract

Aqueous zinc (Zn) batteries hold considerable promise to address safety problems that frequently occur in electric vehicle cells or energy storage applications. However, Zn metal anode suffers seriously from dendrite, corrosion, and interface water decomposition in aqueous electrolytes, especially under large areal capacity or long charging duration. This is mainly because of the uneven longitudinal Zn growth induced by the anisotropic Zn²⁺ diffusion, which is usually neglected in a laboratory study with low areal capacity. Herein, we report an artificial interface of the anodic covalent organic framework (COF, which can be rapidly synthesized and facilely assembled with Zn anode in a large area) to guide the uniform longitudinal Zn growth for dendrite-free Zn batteries. In-situ optical microscope observes that compared with the bare Zn anode, COF interface can promote the formation of the smooth and dendrite-free surface through spatial-triggered uniform longitudinal Zn growth. Theoretical calculation uncovers that anodic COF with a negative charge at its N sites could attract Zn²⁺ to achieve uniform longitudinal Zn²⁺ diffusion. In addition, this COF interface with superior hydrophobicity could suppress water decomposition and Zn corrosion. Consequently, the COF-functionalized Zn anode realizes a high coulombic efficiency under severe Zn plating/stripping conditions (10 mAh cm⁻²), contributing to a long Zn-I<inf>2</inf> full battery life of over 10000 cycles. This work highlights the high-areal-capacity Zn anode protection in external space beyond the interface.