A holistic review of manganese-based redox flow battery chemistries: cell configuration and electrolyte environments

Manganese-based redox couples have garnered significant attention in redox flow batteries (RFBs) for grid energy storage applications, owing to their favorable attributes, including high redox potential, widespread availability, and cost-effectiveness. Nevertheless, their energy density, long-term stability, durability, and cycling stability are often hindered due to the formation and re-deposition of non-conductive MnO2, parasitic hydrogen evolution, internal resistance and restricted electrolyte concentrations. This review highlights the recent advancements in manganese-based redox flow batteries (MRFBs), focusing on the emerging manganese chemistries and their charge-storage mechanisms across diverse electrolyte environments. It also explores the influence of varying cell configurations, flow channel architectures, highlighting how the integration of these factors enhances the overall performance and operational durability of the MRFBs system. In particular Mn-Zn flow battery architectures employing this stabilized redox couple offer a practical balance between energy density and favourable cell voltage. However, achieving broader commercial success will require careful optimization of redox mechanisms, electrolyte engineering, and active material management.