Anhydrous Synthesis of High‐Quality Prussian Blue in Deep Eutectic Solvents for Na‐Ion Batteries

Prussian blue analogs are considered a prospective cathode material for sodium‐ion batteries (SIBs), and the water molecule is an important factor affecting their crystal structure and sodium storage performance. This work synthesizes high‐quality Prussian blue (PB‐ANF) using the anhydrous Na 4 Fe(CN) 6 precursor in an anhydrous deep eutectic solvent. The introduction of water molecules during the synthesis process of PB leads to inhomogeneous crystal growth and more vacancy defects, whereas anhydrous synthesis effectively improves the structural integrity and stability. PB‐ANF delivers a high specific capacity of 167 mAh g −1 at 0.5 C and 128 mAh g −1 at 30 C, and maintains 70% capacity after 500 cycles at 10 C. The outstanding sodium storage properties of PB‐ANF originate from the robust structure formed without the disturbance of H 2 O during the crystal growth. This study offers an innovative anhydrous synthesis strategy for the design of high‐performance Prussian blue as the cathode in SIBs.