Medium-mediated high-crystalline Prussian blue toward exceptionally boosted sodium energy storage

Prussian blue and its analogues (PB/PBAs) represent a promising community of low cost and high capacity cathode materials for sodium ion batteries. Nevertheless, the synthesis-induced crystal deficiencies in the framework of PB/PBAs greatly degrade their sodium energy properties, which challenges the potential practicability. Herein, we demonstrate an effective strategy to regulate the PB crystallinity with advanced sodium energy by tuning the synthesis medium. A favorable agent of sodium polyacrylate is screened out as the reaction mediator, which creates a strong coordinating and highly viscous environment to produce high-crystalline PB (HC-PB). Remarkably, the HC-PB harvests an elevated capacity of 140 mAh g–1 at 0.2 C, superb rate capability (105 mAh g–1 at 30 C), and prominent capacity retention of 94.6 % over 1000 cycles at 10 C. The combination of in situ mechanistic and kinetic analyses reveals the rooting reasons for the performance enhancement. This study opens up a prospective and feasible medium-mediated pathway to accelerate the development of PB/PBAs toward sodium chemistry and beyond.