Sodium ion-storage performance of nickel-doped manganese-based Prussian white composited with carbon nanotubes

Prussian white and its analogues are regarded as promising cathode candidates for sodium-ion batteries because of their high capacity, facile synthesis and abundant resource. However, their cyclic lifespans are limited. One of the main reasons is the complex phase transformations of their crystal structure during the insertion/desertion of sodium ions. Herein, nickel-doped manganese-based Prussian white composited with carbon nanotubes were synthesized with the aim to stabilize crystal structure during charging/discharging and consequently enhance cyclic performance. Structural and chemical characterizations indicate that the doped nickel atoms occupy lattice sites of manganese. Electrochemical evaluations indicate that the obtained cubic-structured Na 1.55 Mn 0.94 Ni 0.06 [Fe(CN) 6 ] 0.92 ∙2.74H 2 O/carbon nanotubes delivers a reversible capacity of 98 mAh g −1 with an initial coulombic efficiency of 97% at 1C and still maintains 64 mAh g −1 after 400 cycles. Serial ex situ X-ray diffractions disclose that the nickel-doped manganese-based Prussian white maintains its cubic structure during the insertion/desertion of the sodium ions. No phase transformation is observed except a little variation of the lattice constants. The structural stability enables high cyclic stability. Nickel doping and carbon nanotube composition are efficient ways to improve the electrochemical performance of the manganese-based Prussian white for sodium-ion batteries. Graphical abstract