Rational Design of 3D Hierarchical Fe₃S₄ for Superior Sodium‐Ion Battery Anode Material

Abstract Among various transition metal sulfides, iron‐based sulfides have attracted wide attention due to their abundant resources, low cost, and non‐toxicity, showing considerable research value in the field of secondary batteries. Thereinto, Fe₃S₄ has a high theoretical specific capacity of 785 mAh g⁻¹. However, at present, the research related to Fe₃S₄ anode for sodium‐ion batteries (SIBs) is still in its infancy, and it also suffers from severe volume expansion and limited preparation. Therefore, to further boost its sodium storage potential, the Fe₃S₄@rGO composite with hierarchical structure and carbonaceous network is proposed in this study. Beneficial from the ingenious hierarchitectures and flexible graphene coating, the Fe₃S₄@rGO anode exhibits outstanding sodium storage performance, which can deliver a high capacity of 603 mAh g⁻¹ after 1500 cycles with a superior capacity retention of 98%. The micron flower‐like structure composed of 2D nanosheets can provide sufficient active sites and promote the rapid transport of Na⁺. Meanwhile, the 3D interconnected graphene carbon network makes a crucial contribution to alleviating volume changes and enhancing electrical conductivity. This work reveals the application potential of Fe₃S₄ as an anode electrode for SIBs and provides available insights for the development of other electrode materials.