Cage-Like Porous Prussian Blue as High-Capacity Cathode for Sodium-Ion Batteries

Fast charge-discharge rate sodium-ion batteries (SIBs) can be considered as an ideal alternative candidate to lithium-ion batteries (LIBs) for low-cost and large-scale application. Prussian blue and its analogues (abbreviated as PB) as a cathode material for SIBs were proposed due to the similar working mechanisms with LIBs. However, the early synthesized PBs have suffered capacity fading at long cycles of charge/discharge and high C-rate. In this work, we synthesized a cage-like porous cubic structure (PB-C) via a simple single iron source precipitation method with a reheating process and acid etching. The galvanostatic charge-discharge measurements have shown that a high specific capacity could be maintained at a high C-rate. At 0.2 C, the specific capacity is 112 mA h g(-1), while at 10 C, the specific capacity is 97 mA h g(-1). Also, PB-C showed no obvious capacity fading at the 1000th cycle with more than 85% capacity retention. Cyclic voltammetry analysis at various scan rates proved that the nanoporous structure with a superior specific surface area carries the pseudocapacitance effect, leading to the excellent electrochemical performance. This exceptional performance discloses that the as-prepared cage-like porous PB is one of the potential candidates as a cathode material in low-cost and large-scale applications for practical SIBs.