Synergistically regulating Zn-ion flux and accelerating ion transport kinetics via zincophilic covalent organic framework interlayer for stable Zn metal anode

Abstract

Zn metal is considered as an ideal anode for aqueous zinc-ion batteries (AZIBs) owing to the inherent merits of low cost, high theoretical capacity, and remarkable safety. However, the formation of Zn dendrites and water-induced parasitic reactions hamper the commercialization of AZIBs. Herein, a synergetic strategy to accelerate ion transfer kinetics and regulate Zn-ion flux has been proposed to achieve dendrite-free Zn anodes via a series of zincophilic covalent organic framework (COF) films. The nanoporous and mechanically stable COF films synthesized by the liquid–liquid interfacial polymerization can be straightforward transferred on the Zn foil surface through a dip-coating technique. Benefiting from the affinity between Zn2+ and electron-rich ketone, the zincophilic COF interlayers promote the de-solvation of hydrated Zn2+, simultaneously offer ample Zn2+ transport channels to facilitate rapid diffusion and regulating a homogenous Zn2+ flux, thereby inhibiting the dendritic growth and leading to the uniform Zn deposition. Additionally, the COF films with strong adherence and large surface area effectively separate Zn anodes from bulk aqueous electrolytes, inhibiting the water-induced corrosion reactions. As a result, the symmetric cell with COF-modified Zn anode exhibited a stable cycling lifetime more than 900 h at 1 mA∙cm−2 and 1 mAh∙cm−2, accompanied by a low voltage polarization of merely 74.3 mV. As a simple approach to synergistically restrict Zn-ion flux and enhance ion transport kinetics using zincophilic COF films via interfacial synthesis, this work would provide new insights into developing highly stable Zn anodes.