Ball-milling synthesis of ultrafine NayFexMn1-x[Fe(CN)6] as high-performance cathode in sodium-ion batteries

Manganese hexacyanoferrate (MnPBA) is a promising cathode material for sodium-ion batteries (SIBs). However, the poor electrical conductivity and the structural instability greatly hinder its practical applications in SIBs. In this work, a facile ball-milling method is used to synthesize the ultrafine NayFexMn1-x[Fe(CN)(6)] without additional additives. It shows that the ultrafine particles (similar to 50 nm) favor the fast Na+ diffusion in MnPBA, while Fe-doping can enhance the electrical conductivity and suppress the structure distortion upon Na+ insertion/extraction. Thus, Fe-doped MnPBA demonstrates greatly improved electrochemical stability and kinetics. Especially, Fe-MnPBA/0.4 can deliver a specific capacity of 119 mA h g(-1) at 1 C, corresponding to an energy density of similar to 380 Wh kg(-1) in half-cell. Even at a current density of 30 C, its specific capacity still retains 86 mA h g(-1). Our work provides a facile strategy to massively synthesize the PBAs on a large scale with excellent sodium-ion storage performance. Ultrafine NayFexMn1-x[Fe(CN)(6)] synthesized via a dry-milling method without additives exhibits excellent rate performance and cycling stability. Fe-MnPBA/0.4 can deliver a specific capacity of 119 mA h g(-1) at 0.2 C and retain 86 mA h g(-1) at 30 C.