Construction of polyaniline coated FeMnCu co-doped Prussian blue analogue as cathode for sodium ion battery

Prussian blue crystal of sodium hexacyanoferrate is widely applied as the cathode for sodium ion battery (SIB) due to the features of high specific capacity and easy synthesis. While, the existed coordinated water and vacancy defects will cause the skeleton collapsed and lattice disordered during the cycling process, which lower the coulombic efficiency and shorten the cycle consistency. Furthermore, the inferior electron transport of Fe-HCF further affects the charge-discharge performance. Herein, we designed a high-quality FeMnCu co-doped Prussian blue (PB) crystal and controlled its crystallization process with assistance of citrate. Moreover, a core-shell structure of conductive polyaniline (PANI) coated Prussian blue analogue (FeMnCu@PANI) was constructed. The as-developed FeMnCu@PANI as the cathode for SIB delivers a capacity of 107 mAh g-1 at the current density of 1C and 82 mAh g-1 at 10C. The capacity retention rate reaches ∼90 % at 10C for 500 cycles. This FeMnCu@PANI crystal is nontoxic, high yield, low cost, and suitable for large-scale producing, which has great potential as cathode for SIB with high-capacity retention rate and long service life.