Effect of the Crystalline Structure of CuxMo6S8 on the Capacity of Mg-Based Secondary Batteries

Abstract

Mo6S8 Chevrel-phase (CP) cathode materials, for Mg secondary batteries, have been reported to be better suited and superior to other cathode materials. We synthesized CuxMo6S8 (Cu-CP) by varying the temperature and time and found different crystalline structures of Cu-CP, depending on the time and temperature of the growth process. Using these structures as precursors for preparing cathodes was shown to influence the performance of the electrochemical cell. After etching Cu from Cu-CP, the structure was stabilized as the rhombohedral phase of Mo6S8 (CP). The morphologies of Cu-CP and CP were examined by scanning electron microscopy, and the structures were confirmed using X-ray diffraction. The coin-cell structure was fabricated, and the electrochemical properties of CP were evaluated and compared for different crystalline structures of Cu-CP. The discharge capacities were improved from 84.2 to 122.9 mAh·g–1 as the structure of Cu-CP changed from rhombohedral to triclinic.