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 K2Zn3[Fe(CN)6]2 crystals with a uniform size distribution of ~1 µm 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 K2Zn3[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.