Metal–Organic Framework Derived Fe7S8 Nanoparticles Embedded in Heteroatom‐Doped Carbon with Lithium and Sodium Storage Capability.

Iron sulfides are promising materials for lithium‐ and sodium‐ion batteries owing to their high theoretical capacity and widespread abundance. Herein, the performance of an iron sulfide‐carbon composite, synthesized from a Fe‐based metal–organic framework (Fe‐MIL‐88NH2) is reported. The material is composed of ultrafine Fe7S8 nanoparticles (<10 nm in diameter) embedded in a heteroatom (N, S, and O)‐doped carbonaceous framework (Fe7S8@HD‐C), and is obtained via a simple and efficient one‐step sulfidation process. The Fe7S8@HD‐C composite, investigated in diethylene glycol dimethyl ether‐based electrolytes as anode material for lithium and sodium batteries, shows high reversible capacities (930 mAh g−1 for lithium and 675 mAh g−1 for sodium at 0.1 A g−1). In situ X‐ray diffraction reveals an insertion reaction to occur in the first lithiation and sodiation steps, followed by conversion reactions. The composite electrodes show rather promising long‐term cycling stability and rate capability for sodium storage in glyme electrolyte, while an improved rate capacity and long‐term cycling stability (800 mAh g−1 after 300 cycles at 1 A g−1) for lithium can be achieved using conventional carbonates. [ABSTRACT FROM AUTHOR]