Copper‐Activated Dynamic Lattice Adaptation and Bond Reinforcement for Enhanced Sodium Storage of Prussian Blue Analogs Cathode

Prussian blue analogs (PBAs) have garnered considerable attention as promising cathode materials for sodium‐ion batteries (SIBs) in recent years, owing to their high theoretical capacity, three‐dimensional ionic channels, and low cost. Nevertheless, the electrochemical properties of PBAs are severely compromised by the excessive Fe(CN) 6 vacancies and crystalline water within the structure. Herein, a copper ion (Cu 2+ ) doping strategy is adopted to enhance the structural stability of PBAs, reduce the content of crystalline water, and thereby enhance its high‐rate performance and cyclic durability. In situ XRD and density functional theory (DFT) calculations confirm that the material exhibits dynamic lattice adaptation and reduced Na + migration energy barrier after Cu 2+ doping. Local lattice distortion and electronic reconfiguration resulting from Cu 2+ incorporation enhance the metal–cyano–metal (M─CN─M′) bond strength, significantly improving the rate performance and cycling performance of PBA. Thus, the prepared CuFePB‐2 exhibits a high capacity of 112.2 mAh g −1 at 1C and a retention of 82.0% after 200 cycles. Additionally, even at 20C, it still delivers a capacity of 57.1 mAh g −1 . This work develops a novel strategy to synergistically enhance the rate capability and cycling stability of PBA materials, thereby enabling high‐performance SIBs.