Prussian white analogues as promising cathode for non-aqueous potassium-ion batteries

We prepared Prussian white analogues—K x MFe(CN) 6 ·mH 2 O (M = Fe, Co, Ni, or Cu). These compounds are investigated as cathode materials for potassium-ion batteries with a non-aqueous electrolyte. Each of these materials exhibits different K-ion storage properties with reversible capacity values ranging from 35 to 110 mAh g − 1 at high potentials above 3.2 V vs. K + /K. Among them, FeFe-Prussian white, K 1.68 Fe 1.09 Fe(CN) 6 ·2.1H 2 O, exhibits the highest reversible capacity of 110 mAh g − 1 and stable cycling performance in contrast to rapid capacity fading of other analogues. Our results demonstrate a remarkable potential of this family of cathode materials for the emerging potassium-ion batteries. • We introduce Prussian white analogues, K x M y [Fe(CN) 6 ] z (M = Fe, Co, Ni, Cu), as cathode materials for potassium-ion batteries. • All these Prussian white materials exhibit high reaction potential, promising capacity and cycling performance. • K 1.68 Fe 1.09 Fe(CN) 6 ·2.1H 2 O delivers high discharge potentials, high capacity of 110 mAh g − 1 , and excellent cycling life.