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 (K2MnFe(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 K2MnFe(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 K2MnFe(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 K2MnFe(CN)6 material are attributed to its stable frameworks that benefit from the defect-free structure.