MOF-derived iron sulfide nanocomposite with sulfur-doped carbon shell as a promising anode material for high-performance lithium-ion batteries

Iron sulfides with high theoretical capacity and low cost have attracted wide attention as anode materials for lithium-ion batteries (LIBs). However, their low electrical conductivity and serious volume expansion largely limit their practical application. In the present study, a spindly nanorod Fe7S8@C-S nanocomposite with sulfur-doped and carbon-coated is synthesized by in-situ sulfidation of Fe-based metal organic framework (Fe-MOF). By virtue of the MOF-derived hierarchical structure, the synthesized Fe7S8@C-S is expected to exhibit outstanding lithium-storage performance and structural stability. As a result, the Fe7S8@C-S delivers a high reversible specific capacity (1503 mAh g-1 at 0.05 A g-1 after 100 cycles), excellent rate capacity, and long-life cycling stability (almost 95% storage retention after 1000 cycles at a large current density of 2.0 A g-1) as an LIB anode. When this anode is matched with an LiCoO2 cathode, the full cell delivers a remarkable discharge capacity (240 mAh g-1 at 0.5 C) and impressive cycling stability (capacity retention of 88% after 200 cycles). Moreover, the lithiation-delithiation mechanism and diffusion kinetics are analyzed to determine the basic principles of the electrochemical reaction and the crucial factors associated with the improved performances.