Co9 S8 /Co as a High-Performance Anode for Sodium-Ion Batteries with an Ether-Based Electrolyte.

Co9 S8 has been regarded as a desirable anode material for sodium-ion batteries because of its high theoretical capacity. In this study, a Co9 S8 anode material containing 5.5 wt % Co (Co9 S8 /Co) was prepared by a solid-state reaction. The electrochemical properties of the material were studied in carbonate and ether-based electrolytes (EBE). The results showed that the material had a longer cycle life and better rate capability in EBE. This excellent electrochemical performance was attributed to a low apparent activation energy and a low overpotential for Na deposition in EBE, which improved the electrode kinetic properties. Furthermore, EBE suppressed side reactions of the electrode and electrolyte, which avoided the formation of a solid electrolyte interphase film.