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 (K(2)Mn[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 K(2)Mn[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 K(2)Mn[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 K(2)Mn[Fe(CN)(6)] material are attributed to its stable frameworks that benefit from the defect-free structure.