Prussian Blue Analogs as Battery Materials

Prussian blue analogs have significant promise as active materials for the next generation of battery electrodes with improved cycle life and rate capability. Their useful electrochemical properties include two independent redox centers per unit cell; a nanoporous, open framework for rapid ion conduction; high stability during ion (de) insertion; and structural and electrochemical tunability for diverse applications. Here we share insights into how control of the five main crystallographic features (two transition-metal ions, the inserting ion, defects, and water) imparts control over the ion-insertion reaction. We then identify five key opportunities to expand our understanding of these materials, including the role of water in their ion conduction, modeling, synthesis methods, use as anode materials, and technoeconomics. Further research in these areas will accelerate the development of new, high-performing battery electrodes.