Designing Better Flow Batteries: An Overview on Fifty Years’ Research

Flow batteries (FBs) are very promising options for long duration energy storage (LDES) due to their attractive features of the decoupled energy and power rating, scalability, and long lifetime. Since the first modern FB was proposed by NSNA in 1973, FBs have developed rapidly in extensive basic research on the key materials, stack, demonstration trials, and even commercial implementation. Meanwhile, as prime candidates for the LDES, FBs still meet several challenges for industrialization: cost and performance concerns, which require that we increase the FB duration and consider some "green" and recycle resources. This review aims at providing the milestones in FB development over the 50 years of research and critical analysis of the different types of FB technologies. The directions in the science and engineering of FBs are finally presented with a future goal of achieving FBs' commercialization.