The Influence of Membrane Selection on the Performance of Ionic Liquid-Based Redox Flow Batteries

The development of large-scale energy storage technologies is a key element in the transition to sustainable energy systems, where redox flow batteries (RFBs) are emerging as a promising alternative to conventional systems. The available literature reveals a notable lack of systematic studies evaluating the impact of membranes on the performance of IL-incorporating RFBs, despite this component being crucial for regulating ionic conductivity, minimizing the crossover of active species, and ensuring the operational stability of the system. This review provides a critical analysis of 81 articles published between 2015 and 2025, examining the impact of various membrane types on key parameters including conductivity, thermal and mechanical stability, energy efficiency, and power output. The findings reveal that more than 70% of the reviewed studies do not directly address the function of the membrane, underscoring the need for research focused on designing selective and robust materials for non-aqueous conditions. Finally, knowledge gaps are identified, and development prospects are proposed, along with the standardization of characterization protocols, to accelerate the practical implementation of IL-based RFBs in various scenarios.