Constructing lithium oxysulfide-rich solid electrolyte interphase to shield polysulfides in practical lithium–sulfur batteries

Long-cycling practical lithium–sulfur batteries are hindered by the parasitic reactions between lithium polysulfide (LiPS) intermediates and lithium metal anodes. Solid electrolyte interphase (SEI) on lithium metal anodes plays a crucial role in shielding the parasitic reactions of LiPSs. Herein, a lithium oxysulfide-rich SEI is demonstrated to shield polysulfides for stabilizing lithium metal anodes in working lithium–sulfur batteries. Li₂SO₄ is sustainably released as an additive to introduce abundant lithium oxysulfide components, such as sulfates, sulfites, and other Li₂S_xO_y in SEI. The lithium oxysulfide-rich SEI effectively shields the parasitic reactions of LiPSs and the lifespan of lithium–sulfur batteries increases by 60% under demanding conditions of ultrathin Li anodes (50 μm) and high-loading S cathodes (4.0 mg cm⁻²). Furthermore, a practical 2.59 Ah lithium–sulfur pouch cell with the lithium oxysulfide-rich SEI delivers 25 cycles with an initial specific energy of 352 Wh kg⁻¹. This work provokes insights into the role of lithium oxysulfide in SEI and inspires rational regulation of SEI to stabilize lithium–sulfur batteries.