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

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.