Abstract
Developing a simple, safe, and efficient route for the preparation of nanoparticulate ternary Chevrel phases MxMo6S8 (CPs; where M = metal) is of great interest because of their applications in energy storage and conversion technologies. Owing to its unique structure, CP is a promising candidate for utilization in rechargeable monovalent (Li/Na) and multivalent (Mg and Al) batteries. However, the wide use of these materials is restricted by the prolonged reaction time, the high energy demands required for their synthesis, the complexity of the preparation process, and the ambiguity in the size of the resultant particles. Herein, we report a simple, efficient, and controllable molecular precursor approach for the synthesis of nanoscale CP without the use of hydrogen gas as a reducing agent. A mixture of precursors based on molybdenum and copper dithiocarbamate complexes were subjected to thermolysis in the presence of finely divided molybdenum to furnish the copper CP, Cu2Mo6S8. The successful formation of the Cu2Mo6S8 CP is confirmed by X-ray diffraction analysis and Raman spectroscopy, while the surface chemistry of the material was examined by X-ray photoelectron spectroscopy photon depth profiling via tunable synchrotron radiation. Microscopic characterization results demonstrate that the synthesized material has a homogeneous structure at the nanoscale, in contrast to the microparticles obtained from conventional approaches previously reported. The prepared CP was assessed as active electrode material in Li-ion and Zn-ion rechargeable batteries. Due to its unique nanostructure and high surface area, the ion diffusion length is reduced, resulting in faster kinetics, lower overpotential, and higher capacities compared to that reported for CP-Mo6S8 materials prepared by the conventional method. It is expected that the proposed synthetic strategy, which represents a new and facile route to tailored CPs, can be extended to the preparation of versatile, easily tuneable CP Mo6S8-based electrode materials for a range of applications in energy storage and conversion systems.

Keywords: Chevrel phase, chalcogenides, Molybdenum sulfide, molecular precursors, rechargeable Li and Zn batteries.