Phase Transformations in Na-Rich Prussian White Cathode Materials with Different Morphology

Prussian white is the promising cathode material for rechargeable sodium ion batteries. Here we study phase transitions in commercial Prussian White powder with particle size up to ~10 μm, which was chemically enriched with sodium, and synthesized sodium-enriched Prussian White with particle size of ~1 μm. X-ray diffraction was used to track structural changes during heating up to 250°C. Both powders were found to undergo the transformation of initial rhombohedral phase to dehydrated rhombohedral phase through a formation of cubic phase. Smaller particle size of the synthesized powder leads to more effective dehydration, which decreases temperatures of all phase transitions by ≈10°C compared to commercial Na-enriched Prussian White.