Cyanide Antidote inspired Ecofriendly Preparation of Sodium‐rich, High‐crystallinity Prussian Blue Cathode Materials from a Single‐iron Source Method

Sodium-rich Prussian blue analogs (PBAs) are promising cathode candidates for sodium-ion batteries, offering high crystallinity, excellent electrochemical performance, and low cost. However, traditional hydrothermal synthesis often necessitates acid treatment, which presents a safety risk due to the potential release of toxic hydrogen cyanide (HCN). Inspired by sodium thiosulfate (Na₂S₂O₃) as a known cyanide antidote, we developed a novel synthesis method that mitigates the risks of HCN leakage, yields high-crystallinity products with minimal defects while promoting the formation of sodium-rich PBAs in a reducing atmosphere. The resulting PBAs exhibited excellent electrochemical performance, including a high initial coulombic efficiency of 98 %, a stable discharge capacity of 143 mAh g^-1 at 0.2 C, and a capacity of 101 mAh g^-1 at 5 C, while maintaining 84 % of initial capacity over 1000 cycles. These properties are attributed to improved Na content and crystallinity as well as reduced defects and water of PBAs enabled by Na₂S₂O₃.