Impact of Synthesis Conditions in Na-Rich Prussian Blue Analogues

Sodium-rich iron hexacyanoferrates were prepared by coprecipitation, hydrothermal route, and under reflux, with or without dehydration. They were obtained with different structures described in cubic, orthorhombic, or rhombohedral symmetry, with variable compositions in sodium, water, and cationic vacancies and with a variety of morphologies. This series of sodium-rich Prussian blue analogues allowed addressing the relationship between synthesis conditions, composition, structure, morphology, and electrochemical properties in Na-ion batteries. A new orthorhombic phase with the Na1.8Fe2(CN)(6)-0.7H(2)O composition synthesized by an hydrothermal route at 140 degrees C is reported for the first time, whereas a phase of Na2Fe2(CN)(6)center dot 2H(2)O composition obtained under reflux, previously described with a monoclinic structure, shows in fact a rhombohedral structure.

Automated summary

This study investigated sodium-rich iron hexacyanoferrates prepared by different synthesis methods and their relationship with structure, morphology, and electrochemical properties. A new orthorhombic phase with the Na1.8Fe2(CN)(6)-0.7H(2)O composition was reported for the first time, while a previously described phase with monoclinic structure was found to actually have a rhombohedral structure.