High-Quality Prussian Blue Analogues K2zn3[Fe(Cn)6]2 Crystals as a Stable and High Rate Cathode Material for Potassium-Ion Batteries

High-quality Prussian blue analogues K 2 Zn 3 [Fe(CN) 6 ] 2 crystals with a uniform size distribution of ~1 um have been synthesized via a facile pyrophosphate-assisted crystallization method at room temperature. Owing to its high crystallinity and structural regularity, the as-synthesized high-quality K 2 Zn 3 [Fe(CN) 6 ] 2 crystal can deliver a theoretical one K reversible capacity of 65.3 mAh g −1 at 50 mA g -1 based on [Fe(CN) 6 ] 3− /[Fe(CN) 6 ] 4− , high rate performance and an impressive long-term cycling performance (a capacity retention of 89.3% after 1000 cycles at 500 mA g -1 )，showing great potentials as a low-cost and stable cathode for potassium ion batteries. • A simple and scalable synthesis method is developed to fabricate high-quality K 2 Zn 3 [Fe(CN) 6 ] 2 (HQ-KZnHCF) via a facile pyrophosphate-assisted crystallization method. • The as-synthesized K 2 Zn 3 [Fe(CN) 6 ] 2 showed well-defined cube-shaped microcrystals with a uniform size distribution of ~1 um. • 3.The high-quality K 2 Zn 3 [Fe(CN) 6 ] 2 crystals deliver high capacity, good rate capability and an impressive long-term cycling performance as the cathode for potassium ion batteries. • 4.The K insertion mechanism of the HQ-KZnHCF electrode was uncovered to study the structural evolution at different charge-discharge states by ex situ XRD.