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 Na_yFe_xMn_1-x[Fe(CN)₆] without additional additives. It shows that the ultrafine particles (~ 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 ~ 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 Na_yFe_xMn_1-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.

六氰合铁酸锰（MnPBA）是用于钠离子电池（SIB）的有前途的正极材料。然而，差的电导率和结构不稳定性极大地阻碍了其在SIB中的实际应用。在这项工作中，一种简便的球磨方法被用于合成超细的Na _y Fe _x Mn _1-x [Fe（CN）₆ ]，而无需添加其他添加剂。它表明超细颗粒（〜50nm）的有利于快速的Na ⁺在扩散MnPBA，而Fe掺杂能够提高电导率和钠时抑制结构失真⁺插入/提取。因此，掺铁的MnPBA表现出大大改善的电化学稳定性和动力学。尤其是，Fe-MnPBA / 0.4可以在1 C下提供119 mA h g ^-1的比容量，相当于半电池中〜380 Wh kg ^-1的能量密度。即使在30 C的电流密度下，其比容量仍保持86 mA h g ^-1。我们的工作提供了一种简便的策略，可以大规模大规模合成PBA，并具有出色的钠离子存储性能。

通过无添加剂的干磨法合成的超细Na _y Fe _x Mn _1-x [Fe（CN）₆ ]具有极好的速率性能和循环稳定性。Fe-MnPBA / 0.4在0.2 C时可提供119 mA h g ^-1的比容量，在30 C时可保留86 mA h g ^-1的比容量。