Prussian White Hierarchical Nanotubes with Surface‐Controlled Charge Storage for Sodium‐Ion Batteries

Abstract Coordination compounds such as Prussian blue and its analogues are acknowledged as promising candidates for electrochemical sodium storage owing to their tailorable and open frameworks. However, a key challenge for these electrode materials is the trade‐off between energy and power. Here, it is demonstrate that Prussian white (Na 3.1 Fe 4 [Fe(CN) 6 ] 3 ) hierarchical nanotubes with fully open configurations render extrinsic Na + intercalation pseudocapacitance. The cathode exhibits a capacity up to 83 mA h g −1 at an ultrahigh rate of 50 C and an unprecedented cycle life over 10 000 times for sodium storage. In situ Raman spectroscopy together with in situ X‐ray diffraction analysis reveal that intercalation pseudocapacitance enables full reaction of N ‐Fe III /Fe II sites in Prussian white with a negligible volume expansion (<2.1%). The discovery of surface‐controlled charge storage occurring inside the entire bulk of intercalation cathodes paves a new way for developing high power, high energy, and long life‐span sodium‐ion batteries.