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

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 prepotassiated 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.