With increasing concerns about energy security and environmental issues globally, there has been an increased focus on the move away from fossil-fuel-based energy sources. As a consequence, there have also been significant changes in the energy storage landscape over the past few years. The desire to develop a green and sustainable society and lifestyle has meant that renewable energy sources have made up an increasingly large share of energy consumption. However, the efficient use of renewable energy requires low-cost and long-life energy storage to incorporate it into the traditional grid system. While lithium-ion batteries have been successfully deployed for portable electronics and electric vehicles, the relatively high energy cost and limited ability to decouple power and energy could render that technology uneconomical for long-duration energy storage needed for deep decarbonization.
Fig. 1 Flow battery configuration and representative materials chemistries. a, A typical redox flow battery with redox-active materials dissolved in liquid electrolytes. b, Timeline of important inorganic and organic redox-active materials in the development of redox flow batteries.
Redox flow batteries are a critical technology for large-scale energy storage, offering the promising characteristics of high scalability, design flexibility and decoupled energy and power (Fig. 1a). In recent years, they have attracted extensive research interest, with significant advances in relevant materials chemistry, performance metrics and characterization. The emerging concepts of hybrid battery design, redox-targeting strategy, photoelectrode integration and organic redox-active materials present new chemistries for cost-effective and sustainable energy storage systems. This Review summarizes the recent development of next-generation redox flow batteries, providing a critical overview of the emerging redox chemistries of active materials from inorganics to organics (Fig. 1b). We discuss electrochemical characterizations and critical performance assessment considering the intrinsic properties of the active materials and the mechanisms that lead to degradation of energy storage capacity. In particular, we highlight the importance of advanced spectroscopic analysis and computational studies in enabling understanding of relevant mechanisms. We also outline the technical requirements for rational design of innovative materials and electrolytes to stimulate more exciting research and present the prospect of this field from aspects of both fundamental science and practical applications.
For more details of this work, please see our recent publication in Nature Reviews Chemistry:
Emerging chemistries and molecular designs for flow batteries, https://www.nature.com/articles/s41570-022-00394-6