One-step synthesis of novel core-shell bimetallic hexacyanoferrate for high performance sodium-storage cathode

Recently, the design of core-shell hierarchical architecture plays an important role in improving the electrochemical performance of Prussian blue analogue cathodes (PBAs). Unfortunately, the inconvenient stepwise preparation and the strict lattice-matching requirement have restricted the development of coreshell PBAs. Herein, we demonstrate a one-step synthesis strategy to synthesize core-shell manganese hexacyanoferrate (MnFeHCF@MnFeHCF) for the first time. And the formation mechanism of the core-shell hierarchical architecture is investigated by first-principles calculations. It is found that the as-obtained MnFeHCF@MnFeHCF act out the superior intrinsic natures, which not only can obtain a larger specific surface area and lower Fe(CN) 6 vacancies but also can activate more Na-storage sites. Compared with the manganese hexacyanoferrate (MnHCF), the iron hexacyanoferrate (FeHCF), and even the traditional coreshell nickel hexacyanoferrate (FeHCF@NiHCF) prepared by a stepwise method, the MnFeHCF@MnFeHCF demonstrates a superior rate performance, which achieves a high capacity of 131 mAh g -1 at 50 mA g -1 and delivers a considerable discharge capacity of about 100 mAh g -1 even at 1600 mA g -1 . Meantime, the capacity retention can reach up to nearly 80% after 500 cycles. The improved performances could be mainly originated from two aspects: on the one hand, Mn substitution is helpful to enhance the material conductivity; on the other hand, the core-shell structure with matched lattice parameters is more favorable to enhance the diffusion coefficient of sodium ions. Beside, the structural transformation of MnFeHCF@MnFeHCF upon the extraction/insertion of sodium ions is instrumental in releasing the interior stress and effectively maintaining the integrity of the crystal structure. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study demonstrates a one-step synthesis strategy for the core-shell manganese hexacyanoferrate and investigates its formation mechanism. The core-shell structure of the material exhibits superior electrochemical performance, with higher discharge capacity and better cycling stability compared to materials prepared by traditional methods.