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.