Electrochemical properties of all-solid-state lithium batteries with amorphous MoS3 electrodes prepared by mechanical milling

Abstract

Amorphous molybdenum trisulfide (MoS₃) active materials were successfully prepared by ball milling the mixture of Mo metal and sulfur. The atomic ratio of Mo to S in the starting mixture was 1 : 3. All the diffraction peaks due to the Mo metal and sulfur disappeared in the milled sample. In addition to a halo pattern due to the amorphous structure, it is a broad peak at about 15° that appeared in the diffraction profile obtained by milling for 80 hours. The HR-TEM image revealed that the microstructure of the milled sample was characterized as random distribution of nano-sized domains with the size of 2–3 nm, which consist of crystalline MoS₂ with the layered structure. The DTA curve of the amorphous MoS₃ exhibited no endothermic peaks attributable to the melting of crystalline sulfur. The particle size of the amorphous MoS₃ was about 1 μm. All-solid-state lithium secondary batteries using a sulfide solid electrolyte and the amorphous MoS₃ electrode showed capacities higher than 670 mA h g⁻¹ for 60 cycles. The amorphous MoS₃ had a higher capacity than the cell using the crystalline MoS₂.