A Fe/Mn‐Based Prussian Blue Analogue as a K‐Rich Cathode Material for Potassium‐Ion Batteries

Abstract The reversible intercalation of K+ into graphite has spurred interest in new rechargeable battery chemistries based on potassium ions. The viability of commercializing potassium‐ion batteries (KIBs) is critically dependent on the availability of pre‐potassiated cathode materials, and the compatibility between the electrolyte and electrode components; which have yet to be fully explored. Herein, we report a Fe and Mn based K‐rich Prussian Blue analogue, which can be used as the cathode of rechargeable KIBs to deliver 115 mAh/g of discharge capacity with two voltage plateaus at 3.9 and 4.1 V vs. K+/K in an electrolyte with fluoroethylene carbonate additive. In half‐cell studies, the cyclability of this Prussian Blue analogue was found to depend on the formation of a passivation layer on the anode and the decomposition of the active electrode material at the cathode. This study demonstrates the importance of electrode−electrolyte compatibility in the development of new rechargeable battery chemistries, especially when the evaluation is based on half‐cell studies where potassium metal is used.