Prussian Blue Nanoplates for Potassium Ion Battery Cathode with High Capacity and High Energy Density

Abstract Prussian blue analogues (PBAs) represent as a class of materials with an open framework structure and have been intensively explored as the potential active materials for alkaline‐ion batteries. Here, we present the synthesis of Prussian blue nanoplates designed for use as high performance cathode materials in potassium‐ion batteries. Prussian blue nanoplates were synthesized through a facile solution precipitation route using a highly concentrated potassium citrate solution. The potassium‐rich environment during the synthesis facilitated horizontal growth of the crystals, yielding potassium‐rich Prussian blue nanoplates. The resultant Prussian blue nanoplates exhibited a significantly larger particle size of 600 nm and a reduced specific surface area of 6.8 m 2 g −1 , compared to conventionally synthesized Prussian blue hexahedrons. Half‐cell tests demonstrated that the Prussian blue nanoplates exhibited a high gravimetric capacity of 152.5 mAh g −1 with a nominal voltage 3.952 V at a C‐rate of 0.1 C, yielding an energy density of 602.7 Wh kg −1 . Cycling tests demonstrated high cycling stability of the material, maintaining a capacity of 122.7 mAh g −1 and a nominal voltage of 3.923 V after 200 cycles at 0.2 C. In a full‐cell configuration with graphite anodes, a gravimetric capacity changed from 134.1 mAh g −1 to 108.9 mAh g −1 after 100 cycles at 0.2 C, demonstrating a good cycling stability. This work provides a new insight into the electrochemical properties of Prussian blue nanoplates and highlights their potential as high‐performance cathode materials for potassium‐ion batteries.