This document is a review of redox flow batteries (RFBs), a type of energy storage technology that is gaining attention for its ability to store large amounts of electrical energy efficiently and cheaply. The review discusses the components of RFBs, focusing on the physical processes involved, and examines various redox couples used in these systems. It highlights the importance of understanding kinetic and transport phenomena in RFBs, as well as the challenges and opportunities associated with different chemistries. The review also addresses the need for cost-effective and reliable storage solutions to support the increasing deployment of renewable energy sources, such as solar and wind, which are intermittent and unpredictable. The review covers various RFB chemistries, including iron/chromium, bromine/polysulfide, all-vanadium, vanadium/bromine, hydrogen-based systems, and hybrid redox-flow batteries. It discusses the advantages and disadvantages of each chemistry, as well as the challenges related to crossover, efficiency, and cost. The review also addresses the importance of understanding the kinetics of redox reactions, which is crucial for optimizing the performance of RFBs. The review concludes with a discussion of the potential of RFBs for grid-scale storage and the need for further research to improve their efficiency, cost, and scalability.This document is a review of redox flow batteries (RFBs), a type of energy storage technology that is gaining attention for its ability to store large amounts of electrical energy efficiently and cheaply. The review discusses the components of RFBs, focusing on the physical processes involved, and examines various redox couples used in these systems. It highlights the importance of understanding kinetic and transport phenomena in RFBs, as well as the challenges and opportunities associated with different chemistries. The review also addresses the need for cost-effective and reliable storage solutions to support the increasing deployment of renewable energy sources, such as solar and wind, which are intermittent and unpredictable. The review covers various RFB chemistries, including iron/chromium, bromine/polysulfide, all-vanadium, vanadium/bromine, hydrogen-based systems, and hybrid redox-flow batteries. It discusses the advantages and disadvantages of each chemistry, as well as the challenges related to crossover, efficiency, and cost. The review also addresses the importance of understanding the kinetics of redox reactions, which is crucial for optimizing the performance of RFBs. The review concludes with a discussion of the potential of RFBs for grid-scale storage and the need for further research to improve their efficiency, cost, and scalability.