A Comparative Review of Metal‐Based Charge Carriers in Nonaqueous Flow Batteries

Energy storage is becoming the chief barrier to the utilization of more renewable energy sources on the grid. With independent service operators aiming to acquire gigawatts in the next 10–20 years, there is a large need to develop a suite of new storage technologies. Redox flow batteries (RFB) may be part of the solution if certain key barriers are overcome. This Review focuses on a particular kind of RFB based on nonaqueous media that promises to meet the challenge through higher voltages than the organic and aqueous variants. This class of RFB is divided into three groups: molecular, macromolecular, and redox‐targeted systems. The growing field of theoretical modeling is also reviewed and discussed. Shocking potential: Nonaqueous redox flow batteries exhibit great promise to overcome the voltage and solubility limitations of aqueous systems, and significant progress has been achieved. This Review focuses on contemporary (2015–2020) examples of metal‐based nonaqueous redox flow batteries and is divided between molecular complexes, macromolecular complexes, and redox‐targeting technologies. It also discusses the development and state of the art in the theoretical computational modeling of these systems. Each of the approaches is compared and their future prospects are discussed.