Mechanochemical Synthesis of Amorphous MoSx (x = 3, 4, 5, 6, and 7) Electrode for All-Solid-state Sodium Battery

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-MoSx, 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-MoSx proceeds mainly by anion redox with dissociation and formation of disulfide bonds. Amorphous sulfur-rich MoSx is thus a promising electrode active material with high capacity in all-solid-state sodium batteries. (C) 2022 The Ceramic Society of Japan. All rights reserved.