Fe–P–S electrodes for all-solid-state lithium secondary batteries using sulfide-based solid electrolytes

Abstract Although lithium-sulfur batteries are expected to be the next-generation high-capacity battery of choices, the sulfur electrodes studied so far contain large amounts (typically 30–60 wt%) of carbon additives, resulting in low energy density. In this study, an Fe–P–S-based material is prepared and characterized for the use as a sulfur electrode with a low content of carbon additives. The electrode material based on Fe–P–S is synthesized by the mechanical milling of FePS3 and elemental sulfur. The ball-milled 70FePS3⋅30S (wt%) electrode comprises FeS2 particles of ~30 nm in size and amorphous P–S. The all-solid-state battery operated at 100 °C exhibits a reversible capacity of more than 625 mAh g−1 for 50 cycles at 0.51 mA cm−2 (~0.1C) in spite of the low carbon content (2 wt%) in the electrode. During the discharge-charge cycle, the sulfur component is confirmed to be both reduced and oxidized, cyclically.