Synthesis of Fe-doped Mn-based Prussian blue hierarchical architecture for high-performance sodium ion batteries

Sodium manganese hexacyanoferrates (MnHCFs) have great potential as cathode for sodium-ion batteries (SIBs) owing to their large specific capacity, low cost, ecofriendly synthesis and high working voltage. Nevertheless, their cycling stability is limited by Jahn-Teller effect (JT-effect) of Mn3+, phase transitions and Mn2+ dissolution during the charging and discharging processes. Herein, an unconventional solid-liquid two-phase route is developed to fabricate a novel hierarchical nanostructure Na1.02Mn0.57Fe0.43[Fe(CN)6]0.63∙1·39H2O in view of different solubility of raw material Na4Fe(CN)6·10H2O in the mixed solvent of ethanol and water. Benefiting from unique porous hierarchical architecture, good structural stability, high electrical conductivity and fast capacitive behavior, such Fe-doped MnHCF cathode has an outstanding rate capability with large discharging capacity of 127 mAh g−1 at 25 mA g−1 and 71 mAh g−1 at 1200 mA g−1, and an excellent cyclability with 120 mAh g−1 of specific capacity at 100 mA g−1 and 86% of capacity retention over 200 cycles. In particular, the facile and controllable synthesis process of Fe-doped MnHCFs make it accessible for large-scale applications.