All-solid-state cells were fabricated using Cu x Mo6S8−y Chevrel-phase as an active material and Li2S–P2S5 glass–ceramics as a solid electrolyte. The cells showed good cycle performance with a constant capacity of about 100mAhg−1 for 2000 cycles at the current density of 1.28mAcm−2 at room temperature. The reaction mechanism in the all-solid-state cells was investigated using X-ray diffraction (XRD). The XRD pattern after the 100th charge was almost identical to that before cycling; it is therefore considered that the retention of the crystal structure during cycling brings about a good cycle performance. The use of Cu x Mo6S8−y as an electrode and Li2S–P2S5 glass–ceramics as a solid electrolyte led to the formation of a good solid–solid interface using impedance spectroscopy. All-solid-state cells using Cu x Mo6S8−y as an active material and the 70Li2S·30P2S5 (mol%) glass–ceramic as a solid electrolyte worked at a high current density of 12.8mAcm−2 at a high temperature of 160°C and retained a reversible capacity of about 270mAhg−1 for 10 cycles.