Boosting Sodium Storage in Prussian Blue Analogs Through Iron Vacancies and Copper Doping

Abstract Prussian Blue Analogs (PBAs) have shown considerable prospects as the cathode materials for sodium‐ion batteries (SIBs) on account of their high theoretical capacity, low cost, and easy preparation. The low practical capacity and poor cycling stability of PBAs, however, limit their wide practical deployment. To address these issues, a new strategy is deployed through introducing Fe vacancies and Cu‐dopant into the PBAs frame structure, boosting the specific capacity and improving the cycling stability. On the one hand, the introduction of Fe vacancies in PBA (PBA□Fe) can provide additional storage sites and facilitate Na + diffusion kinetics, yielding a high capacity of ≈164 mAh g −1 at a low current density which approaches the theoretical capacity. On the other hand, the Cu‐dopant is further helpful in stabilizing the structure of PBA□Fe, thus improving the cycling stability. This work paves a new strategy that enables unlocking the capacity and improving the cycling stability of PBA materials toward high‐performance SIBs.