Long life and high-rate Berlin green FeFe(CN)6 cathode material for a non-aqueous potassium-ion battery

High-quality sized FeFe(CN)₆ delivered a reversible capacity of 124 mA h g⁻¹ at the current rate of 0.5C for KIB, and still retained a reversible capacity of 93 mA h g⁻¹ at 5C with a coulombic efficiency of 100%.