Sequentially epitaxial multi-shelled Mn-based Prussian blue cathode for highly stable sodium-ions batteries

The sodium manganese hexacyanoferrate (MnPB) has drawn widely attention as a remarkable cathode material for sodium-ions batteries owing to its high theoretical capacity (∼170 mAh g−1), environmental-friendly and low cost. However, it suffers from serious capacity fading and inferior cycling stability caused by the inevitable Jahn-Teller distortion and significant volume change during Na+ insertion/extraction process. Herein, we propose a simple one-pot method for constructing a multi-shelled Mn-based Prussian blue through sequentially epitaxial growth CoPB and NiPB on the surface of MnPB (NiCoMnPB). The density functional theory calculations demonstrate the unequal affinities of different metal ions with various chelating agents (citrate and ferrocyanide), leading to the dissociation and recombination of metal ions and chelating agents in a certain order. Effectively inheriting merits of CoPB and NiPB, the NiCoMnPB reveals enhanced charge transfer kinetics, suppressed volume change and alleviative Jahn-Teller distortion during cycling, thereby exhibiting superior rate capacity (∼54.2 mAh g−1 at 3200 mA/g), long-term cyclic stability and capacity retention (∼76% over 1000 cycles at 800 mA/g). This work provides a simple method to construct multi-shelled PBAs, which can integrate the virtues of different materials to ameliorate the electrochemical properties of initial materials.