A review of current developments in non-aqueous redox flow batteries: characterization of their membranes for design perspective
The non-aqueous redox flow battery (RFB) is one of the emerging large-scale energy storage systems that may overcome the low energy density limited by breakdown of water at a high voltage in aqueous RFBs. Yet development of the non-aqueous RFB is at an early stage, so its components are not thoroughly understood. As a key component of non-aqueous RFBs, the role of the membrane is to suppress cross-contamination between the anolyte and catholyte confined in two separate compartments, and to transport the charge carrier ions selectively for the completion of the circuit during cell operation. In this review, recent studies on non-aqueous redox flow systems are summarized including redox couples, electrolytes, and systems including membranes. A focus is placed on comparison of battery performance in terms of the current and power density through membranes. In addition, we introduce syntheses and characterization of membranes used for non-aqueous RFBs.