Introducing Zinc Ion into Manganese-Based Prussian Blue for Improving the Structural Stability of Sodium-Ion Battery Cathode

Manganese-based Prussian blue (MF-N) is a promising cathode material for sodium-ion batteries, which has attracted wide attention due to its advantages of high specific capacity and low cost. However, the lattice channel instability of MF-N during sodium ion de-intercalation leads to drastic phase transitions, structural damage, particle cracking, and cyclic stability failure. Considering divalent zinc ion has a strong electrostatic interaction with the crystal structure of the cathode material and presents no electrochemical activity in the corresponding electrochemical window, it can effectively stabilize the lattice channel and structure of MF-N. Thus zinc ions are introduced into the structure of MF-N to replace sodium ions on the lattice channel by the co-precipitation method. The phases of manganese-based Prussian blue with zinc ion (MF-NZ) are cubic and tetragonal when the sodium ions are completely extracted due to the presence of zinc ions supporting the lattice channel, which inhibits the complete transformation of the phase to tetragonal and makes MF-NZ exhibit excellent structural stability. The MF-NZ cathode delivers a capacity of 104.7 mAh g-1 even at 5 C and retains a capacity of 88.1 mAh g-1 in 300 cycles at 1 C, which is 133.7% and 113.8% higher than those of MF-N respectively. This study provides a feasible strategy for minimizing structural destruction and improving the electrochemical performances of MF-N cathode.