Structurally Stable, Low H2O Prussian Blue Analogs toward High Performance Sodium Storage

Abstract Prussian blue analogues (PBAs) are recognized as promising cathode materials for sodium‐ion batteries (SIBs) due to their facile synthesis, low‐cost, high capacity, and environmental friendliness. However, high water content (>10 wt%) in the framework and unsatisfactory structural stability of PBAs are still the bottlenecks for industrial applications. Herein, interstitial K‐doping is employed to minimize the interstitial water and enhance the structural stability of Na 2‐x FeMn[Fe(CN) 6 ] (FeMnPBA), thereby boosting the sodium storage performance. The 3% K‐doping (K‐FeMnPBA3) demonstrates a much‐reduced water content of 6.9%, accompanied by a notably enhanced capacity of 139.1 mAh g −1 at 100 mA g −1 and a remarkable capacity retention of 77.1% after 700 cycles. Furthermore, the K‐FeMnPBA3/hard carbon (HC) pouch cell achieves a stable cyclability with 82.6% capacity retention after 600 cycles. This research offers valuable insights into low‐water PBAs for practical applications in SIBs.