Scalable Mechanochemical Synthesis of High-quality Prussian Blue Analogues for High-Energy and Durable Potassium-Ion Batteries

Abstract

Prussian blue analogues (PBAs) are recognized as promising cathode materials for potassium-ion batteries (PIBs), particularly the low-cost and high-energy K₂Mn[Fe(CN)₆](KMnF). However, conventional solution-based synthesis inevitably introduces [Fe(CN)₆]^4- defects and lattice water while suffering low synthesis efficiency, unfavorable to the improvement of electrochemical performance and scalability. In this work, we report a simple solvent-free mechanochemical strategy for the synthesis of a wide variety of K₂M[Fe(CN)₆] (M=Mn, Mg, Ca, etc.) with negligible defects and water, and it is unprecedented to achieve the kilogram-level products of high-quality KMnF within just 10 minutes. The as-prepared KMnF delivers a high energy density of 590 Wh kg^-1 at 0.2 C and exhibits an astonishing stability over 10,000 cycles and rate ability up to 50 C in potassium metal half-cell. Encouragingly, a high-areal-capacity pouch cell with 2.2 mAh cm^-2 (16.5 mg cm^-2) exhibits a capacity retention of 80.7 % after 500 cycles. Furthermore, systematic in-situ characterization reveals underlying mechanism insights into structure-performance relationships. Specifically, the fully coordinated Mn-N₆ octahedral configuration effectively suppresses Mn³⁺ Jahn-Teller distortion, enabling reversible phase transitions under both high-voltage and long-term cycling conditions. In addition, minimal defects provide sufficient redox centers, while the continuous three-dimensional framework facilitates rapid K⁺ diffusion kinetics. This work provides a new opportunity for the ultrafast, universal and scalable synthesis of high-quality PBAs, facilitating the practical application of PIBs while enabling precise structural and compositional design of novel PBAs.