Progress of Prussian Blue and Its Analogues as Cathode Materials for Potassium Ion Batteries

Environmental pollution and the energy crisis have promoted the development of clean energy as well as new‐generation energy storage systems. Potassium ion batteries (PIBs) have emerged as a possible alternative to lithium‐ion batteries due to their abundant reserves, low cost, and impressive electrochemical performance. However, the search for suitable cathode materials has become particularly crucial. Recently, Prussian blue (PB) has been investigated as a potential cathode material for PIBs, which has an open three‐dimensional framework to accommodate a large volume of potassium ions and adjustable composition for different applications. In this review, Prussian blue and its analogues (PBAs) and their application in PIBs were summarized detailly. We presented the composition, structure, potassium ion storage mechanism, preparation process of PBAs, and then focus on the performance optimization methods of the PBAs, including transition metal doping and conductive material adding into PBAs. Finally, the challenges as well as the outlook on the future development of PBAs were proposed for further application in this battery system. In potassium ion batteries with Prussian blue and its analogs as cathodes, the performance of the batteries can be optimized by various pairs of methods. These include improving the preparation process, doping with a variety of transition metals, and compounding with conductive materials. The enhancement of performance helps to promote the large‐scale application of potassium ion batteries.