Mechanochemical synthesis of amorphous MoS_x (x = 3, 4, 5, 6, and 7) electrode for all-solid-state sodium battery

抄録

All-solid-state sodium secondary batteries have garnered significant attention as next-generation batteries with high safety. To realize an all-solid-state sodium secondary battery with a high energy density, it is necessary to develop a high-capacity electrode active material. In this study, we prepared amorphous molybdenum polysulfide (a-MoS_x, x = 3–7) using a mechanochemical process as electrode active material in all-solid-state cells using Na₃PS₄ sulfide electrolyte. In all-solid-state cells, a-MoS₃, a-MoS₄, a-MoS₅, a-MoS₆, and a-MoS₇ showed high reversible capacities of 260, 330, 470, 540, and 510 mAh g⁻¹, respectively. X-ray photoelectron spectroscopy analyses suggested that the discharge–charge reaction in a-MoS_x proceeds mainly by anion redox with dissociation and formation of disulfide bonds. Amorphous sulfur-rich MoS_x is thus a promising electrode active material with high capacity in all-solid-state sodium batteries.