Electrochemical Properties of All-solid-state Lithium Batteries with Amorphous FeS_x-based Composite Positive Electrodes Prepared via Mechanochemistry

Abstract

Iron sulfide (FeS_x) composite positive electrodes were prepared mechanochemistry and applied to all-solid-state lithium cells. The prepared composites, consisting of Fe, S, Li₃PS₄ solid electrolyte (SE), and vapor-growth carbon fiber (VGCF), were in amorphous state after ball milling for 10 h. An all-solid-state cell with an amorphous Fe-S-SE-VGCF composite as the positive electrode exhibits a high reversible capacity of 420 mAh per total weight of the composite electrode at a current density of 0.13 mA cm⁻² at 25°C. The cell exhibited a capacity retention of 88% after 200 cycles at a current density of 0.64 mA cm⁻² at 25°C. The all-solid-state cell using the Fe-S-SE-VGCF composite at a current density of 0.13 mA cm⁻² at 100°C exhibited a higher reversible capacity of 550 mAh g⁻¹. The Fe-S-SE-VGCF composite is thus a promising positive electrode material, with high capacity and good cycle performance for all-solid-state lithium secondary batteries.