Sodium manganese hexacyanoferrate as Zn ion host toward aqueous energy storage

Abstract Aqueous Zn-ion batteries (ZIBs), a new green energy storage system, have enormous development potential among various aqueous batteries due to the superiorities of good environmental friendliness, low production costs, high operational safety, high theoretical capacity, and excellent rate performance. Compared with traditional cathode materials like manganese oxides and vanadium oxides, Prussian blue analogues (PBAs) with a firm 3D framework and large ion channels are more suitable for zinc ions insertion/extraction. Here, environmentally friendly sodium manganese hexacyanoferrate (NaMnHCF) is applied to aqueous ZIBs, and its excellent electrochemical performance is characterized by varieties of analytical techniques. The charge/discharge profiles display a rather flat operating platform with extremely small redox polarization (less than 0.05 V). Under the current density of 50 mA g−1, NaMnHCF can attain an initial charged specific capacity of 55.3 mAh g−1. Meanwhile, it also exhibits a superior electrochemical rate performance. Furthermore, the mechanism of zinc ions insertion/extraction in the NaMnHCF frameworks is revealed through a deep exploration of the relationship between element states, storage kinetics, crystal structure, and electrochemical properties. From a practical standpoint, the environmentally friendly NaMnHCF exhibits favorable rate capability and cycling stability, which makes it be a perfect choice for aqueous ZIBs of the application in the green new energy industry.