A Co9S8/C nanocomposite is prepared using a solid-state reaction followed by a facile mechanical ball-milling treatment, with sucrose as the carbon source. The phases, morphologies, and detailed structures of the Co9S8/C nanocomposite are well-characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. When evaluated as an anode material for sodium-ion batteries, the Co9S8/C nanocomposite electrode displays a reversible capacity of similar to 567 mA h g(-1) in the initial cycle and maintains a reversible capacity of similar to 320 mA h g(-1) after 30 cycles, indicating a larger capacity and a stable cycling performance. For comparison, the electrochemical performances of Co9S8 and Co9S8/C samples synthesized using the solid-state reaction are also displayed. The ex demonstrate that Co9S8 undergoes a conversion-type sodium storage mechanism. situ XRD and transmission electron microscopy tests demonstrate that Co9S8 undergoes a conversion-type sodium storage mechanism.