Preparation high-performance cathode of vacancy-free Prussian blue analogues for sodium ion batteries by directional capture of free Mn-ion

To address the issue of poor cycling performance and capacity of Mn-based Prussian Blue analogues (PBAs) as sodium ion battery cathodes due to the solubility of Mn ions, this study utilizes the strong chelating property of EDTA2- with Mn ions to hydrothermally modify the sodium-rich monoclinic Na1.75Mn[Fe(CN)6]0.94 & sdot;2.25H2O synthesized under high salt conditions, in order to enhance its capacity and stability. The modified Na1.93Mn[Fe (CN)6]center dot 2 & sdot;.38H2O exhibits a discharge capacity of 156.16 mAh/g at 10 mA g-1 (91.86 % of the theoretical capacity), it still retains the highest discharge capacity (70.23 mAh/g) after 500 cycles at 100 mA g-1. Based on experimental analysis, the improvement in the electrochemical performance of PBAs was attributed to three main factors: (1) enhanced Na content; (2) suppression of defects; and (3) improved crystal structure.