Preparation and Evaluation of Co-Doped Fe 7 S 8 /C Composites for Lithium Storage.

Fe 7 S 8 has a high theoretical capacity (663 mAh g -1 ) and can be prepared at a low cost, making it advantageous for production. However, Fe 7 S 8 has two disadvantages as a lithium-ion battery anode material. The first is that the conductivity of Fe 7 S 8 is not good. The second is that when the lithium ion is embedded, the volume expansion of the Fe 7 S 8 electrode is serious. That is why Fe 7 S 8 has not been used in real life yet. In this paper, Co-Fe 7 S 8 /C composites were prepared by doping Co into Fe 7 S 8 through a one-pot simple hydrothermal method. In situ Co is doped into Fe 7 S 8 to produce a more disordered microstructure to improve ion and electron transport performance, thereby reducing the activation barrier of the main material. The Co-Fe 7 S 8 /C electrode presents a high specific discharge capacity of 1586 mAh g -1 and a Coulombic efficiency (CE) of 71.34% at an initial cycle at 0.1 A g -1 . After 1500 cycles, the specific discharge capacity remains at 436 mAh g -1 (5 A g -1 ). When the current density returns to 0.1 A g -1 , the capacity almost returns to the initial level, showing excellent rate performance.