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 EDTA 2− with Mn ions to hydrothermally modify the sodium-rich monoclinic Na 1.75 Mn[ Fe ( CN ) 6 ] 0.94 ·2.25H 2 O synthesized under high salt conditions, in order to enhance its capacity and stability. The modified Na 1.93 Mn[Fe(CN) 6 ]•2·.38H 2 O 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.