In Situ Construction of “Anchor‐Like” Structures in FeNCN for Long Cyclic Life in Sodium‐Ion Batteries

Abstract Iron carbodiimide (FeNCN) is a high‐reactivity anode material for sodium‐ion batteries. However, strict synthesis technology and poor electrochemical stability limit its application. FeNCN polyhedrons are prepared using a facile one‐step pyrolysis process. In these polyhedrons, many “anchor‐like” structures are in situ constructed with FeC bonds. These FeC bonds connect the FeNCN polyhedrons closely. The FeNCN polyhedrons with “anchor‐like” structures exhibit good electrochemical stability, that is, high capacity retention of 79.9% (408 mAh g −1 ) at 0.5 A g −1 after 300 cycles. Further analysis suggests that the FeC bond plays an important role to improve the structural stability of FeNCN polyhedrons. The “anchor‐like” structures with FeC bonds can hold FeNCN polyhedrons closely when Na + intercalates, avoiding structural breakage with obvious capacity loss. This work provides a novel synthesis technology of FeNCN and helps related researcher to deepen the understanding of this material, as well as provide inspirations as to improving the electrochemical stability of related materials.