Highly Crystallized Na2CoFe(CN)6 with Suppressed Lattice Defects as Superior Cathode Material for Sodium-Ion Batteries

Prussian blue and its analogues have received particular attention as superior cathodes for Na-ion batteries due to their potential 2-Na storage capacity (similar to 170 mAh g(-1)) and low cost. However, most of-the Prussian blue compounds obtained from the conventional synthetic routes contain large amounts of Fe(CN)(6) vacancies and coordinated water molecules, which leads to the collapse of cyano-bridged framework and: serious deterioration of their Na-storage ability. Herein, we propose a facile citrate-Assisted controlled crystallization method to obtain low-defect Prussian-blue lattice with greatly improved Na-storage capacity and cycling stability. As an example, the as-prepared Na2CoFe(CN)(6) nanocrystals demonstrate a reversible 2-Na storage reaction with a high specific capacity of 150 mAh g(-1) and, a similar to 90% capacity retention over 200 cycles, possibly serving as a low cost and high performance cathode for Na-ion batteries. In particular, the synthetic strategy described in this work may be extended to other coordination-framework materials for a wide range of energy conversion and storage applications.