Metal–Organic Framework-Based Membranes with High Selectivity for Non-Aqueous Redox Flow Battery

Abstract

The advancement of non-aqueous redox flow batteries (NARFBs) remains significantly constrained by the absence of membranes with sufficient ionic selectivity and chemical compatibility. Herein, we fabricated flexible membranes incorporating metal–organic framework (MOF) via a solution casting approach. The rigid framework structure of the MOF effectively suppresses membrane swelling in organic solvents. The appropriate structural pore of MOF enables a size-sieving effect toward redox-active materials and supporting electrolyte, thereby reducing material crossover and enhancing the ionic selectivity of the composite membranes. The batteries with the designed composite membranes exhibit a Coulombic efficiency of higher than 99% and significantly improved cycling stability at 10 mA cm−2. The membrane design strategy, employing MOF materials with a structural pore size between the molecular size of the supporting electrolyte and active materials, is universal for NARFB.