Continuous Conductive Networks Built by Prussian Blue Cubes and Mesoporous Carbon Lead to Enhanced Sodium-Ion Storage Performances

The challenges of improving electrical conductivities and enhanced rapid dynamics are active research areas in the modification of Prussian blue (PB) and Prussian blue analogues (PBAs), which are used as excellent cathodes of sodium-ion batteries (SIBs). Herein, the terephthalic acid etched stepwise hollow bulky PB cubes and the intimate contact mesoporous carbon (CMK-3) particles with the adhered minisize PB cubes can together build continuous conductive networks. The composite (donated as N-PB@CMK) has high electrical conductivity, low resistance, and ultrahigh specific surface, which can lead to high capacitive contribution ratios. The N-PB@CMK electrode can deliver a discharge capacity of 120 mAh g^-1 and maintain retention of 85.0% after cycling for 200 cycles at a current density of 100 mA g^-1. Even cycling at 1 A g^-1, the reversible capacity can be measured to 102 mAh g^-1 and exhibit stability over a long cycle. In situ Raman spectroscopy and X-ray diffraction (XRD) patterns were further measured to illustrate the phase transition of crystal structure along with the extraction/insertion processes of Na⁺ ions. Especially, the assembled full cell with NaTi₂(PO₄)₃@C anode can also show good stability and provide promising insights of applying the N-PB@CMK for energy storage systems in the future.