A comprehensive review of metal-based redox flow batteries: progress and perspectives

Redox flow batteries (RFBs) are perceived to lead the large-scale energy storage technology by integrating with intermittent renewable energy resources such as wind and solar to overcome current challenges in conventional energy storage devices. Recently, several modifications have been employed in the development of RFBs to achieve efficient energy storage at an economically acceptable cost of the system. For large-scale deployment, further improvement in energy efficiency, longevity of the system, and reduction in cost are required. Most of the recent research activities are focused on the discovery of new materials to increase RFBs' energy storage-release performance with long-term stable operations suitable for implementation in mobile devices. Considering the growth in research interest, and the volume of literature generated over the past decade on the topic, a review article highlighting the key development and status of research is essential. Herein, we intend to provide the basics of the RFB system including their cell components, various types, and the current trends highlighting the study gaps that require extra effort. Moreover, we conducted an analysis of the cost of the RFBs, associated challenges, and mitigation strategies. The review also includes electrode/electrolyte materials in a table format for quick access for comparison purposes.