Surface Modification of Fe7S8/C Anode via Ultrathin Amorphous TiO2 Layer for Enhanced Sodium Storage Performance

Abstract Iron sulfides with high theoretical capacity and low cost have attracted extensive attention as anode materials for sodium ion batteries. However, the inferior electrical conductivity and devastating volume change and interface instability have largely hindered their practical electrochemical properties. Here, ultrathin amorphous TiO 2 layer is constructed on the surface of a metal–organic framework derived porous Fe 7 S 8 /C electrode via a facile atomic layer deposition strategy. By virtue of the porous structure and enhanced conductivity of the Fe 7 S 8 /C, the electroactive TiO 2 layer is expected to effectively improve the electrode interface stability and structure integrity of the electrode. As a result, the TiO 2 ‐modified Fe 7 S 8 /C anode exhibits significant performance improvement for sodium‐ion batteries. The optimal TiO 2 ‐modified Fe 7 S 8 /C electrode delivers reversible capacity of 423.3 mA h g −1 after 200 cycles with high capacity retention of 75.3% at 0.2 C. Meanwhile, the TiO 2 coating is conducive to construct favorable solid electrolyte interphase, leading to much enhanced initial Coulombic efficiency from 66.9% to 72.3%. The remarkable improvement suggests that the interphase modification holds great promise for high‐performance metal sulfide‐based anode materials for sodium‐ion batteries.