The electrochemical performance of all-solid-state cells using Mo-S Chevrel-phase compound in the wide operating temperature range from -30 degrees C to 160 degrees C was investigated. The cells showed the capacity of about 200 mAh g(-1), which is higher than the theoretical capacity of CuxMo6S8-y active material at temperatures over 100 degrees C. TEM observation of the electrodes after cycle tests at high temperature indicated that Cu diffused from the active material into the Li2S-P2S5 solid electrolytes and this would be mainly responsible for the excess capacity and a poor cyclability at the high temperatures. The use of Mo6S8-y active materials prepared by removing Cu from CuxMo6S8-y chemically, improved cycle performance of the cells at the high temperatures. The addition of acetylene black (AB) in CuxMo6S8-y electrodes is effective in suppressing the diffusion of Cu into the solid electrolytes, and thus the cells using the composite electrode with CuxMo6S8-y, Li2S-P2S5 electrolytes and AB maintained the reversible capacity of about 190 mAh g(-1) at 60 (irate at 160 degrees C for 100 cycles. Mo-S Chevrel-phase compound is promising for the electrode materials in all-solid-state cells with the outstanding electrochemical performance at wide operating temperatures. (C) 2013 The Electrochemical Society. All rights reserved.