A multifunctional separator decorated by anionic metal–organic framework toward ultrastable zinc anodes

Abstract

Aqueous zinc ion batteries (AZIBs) have excellent development prospects due to their high theoretical capacity and low cost. Nevertheless, the commercial separator represented by glass fiber (GF) in AZIBs usually exhibits uneven porosity, poor zincophilicity, and insufficient functional groups, resulting in the emergence of the zinc anode dendrites and side reactions. Designing a separator with specific interfacial ion transport behavior is essential to achieve a highly stable reversible zinc anode. Herein, an anionic metal–organic framework (MOF) functionalized separator (GF-Bio-MOF-100) was presented to accelerate the desolvation process and modulate Zn²⁺ flux, thereby delivering the decreased nucleation overpotential and uniform Zn²⁺ deposition. The in-depth kinetics investigations combined with the in-situ Raman spectroscopy demonstrate that the carbonyl group within the Bio-MOF-100 is capable of capturing the H₂O molecules of [Zn(H₂O)₆]²⁺ via the H-bond interaction, which further accelerates the desolvation process and transport kinetics of Zn²⁺. Meanwhile, the anionic framework of the GF-Bio-MOF-100 separator acts as an interfacial ion channel to regulate the Zn²⁺ flux and enables dendrite-free Zn²⁺ deposition and growth. Consequently, the Zn|GF-Bio-MOF-100|Zn symmetric cell exhibited a stable Zn²⁺ plating/stripping behavior and it could cycle for 2000 h at 0.3 mA cm⁻². Additionally, the assembled Zn|GF-Bio-MOF-100|MnO₂ full cell delivers a capacity retention of 83.9% after 1000 cycles at 0.5 A g⁻¹. This work provides new insights into the design of functionalized separators for long-life AZIBs.