High performance all-solid-state lithium/sulfur batteries using lithium argyrodite electrolyte

Among the known fast Li+ ion conducting solids, thiophosphates and especially lithium argyrodites Li6PS5 X (X = Cl, Br) exhibit a great potential due to their high ionic conductivities and electrochemical stability. Here, we prepare all-solid-state lithium secondary batteries combining sulfur as the active cathode material with argyrodite-type Li6PS5Br as the solid electrolyte. Composite cathode powder of sulfur, Li6PS5Br and super P carbon are fabricated by a two-step ball milling at high rotating speed of 500 rpm, yielding a uniform composite cathode mixture with a particle size smaller than 100 nm. The resulting all-solid-state S/Li6PS5Br/In-Li batteries with S contents varied over the range of 20-40 wt% show a maximum capacity of 1460 mAh/g (with respect to the weight of sulfur) and a reversible capacity of up to 1080 mAh/g after 50 cycles at C/10 rate. Ex situ X-ray diffraction (XRD) results demonstrate that Li6PS5Br undergoes no structural change throughout the cycling.