Defect-free potassium manganese hexacyanoferrate cathode material for high-performance potassium-ion batteries

Potassium-ion batteries (KIBs) are promising electrochemical energy storage systems because of their low cost and high energy density. However, practical exploitation of KIBs is hampered by the lack of high-performance cathode materials. Here we report a potassium manganese hexacyanoferrate (K₂Mn[Fe(CN)₆]) material, with a negligible content of defects and water, for efficient high-voltage K-ion storage. When tested in combination with a K metal anode, the K₂Mn[Fe(CN)₆]-based electrode enables a cell specific energy of 609.7 Wh kg^-1 and 80% capacity retention after 7800 cycles. Moreover, a K-ion full-cell consisting of graphite and K₂Mn[Fe(CN)₆] as anode and cathode active materials, respectively, demonstrates a specific energy of 331.5 Wh kg^-1, remarkable rate capability, and negligible capacity decay for 300 cycles. The remarkable electrochemical energy storage performances of the K₂Mn[Fe(CN)₆] material are attributed to its stable frameworks that benefit from the defect-free structure.