▎ 摘　　要

NOVELTY - Protective layer, comprises precursor solution of the interface protection layer including lithium salt, ether solvent and initiator in a mass ratio of (10-100):100:(0.01-1). The lithium salt is lithium trifluoromethanesulfonylimide (LiTFSI) and ether solvent is 1,3-dioxolane (DOL), and the initiator is iron trifluoromethanesulfonate (Fe(OTf )3). USE - The protective layer is useful for cathode interface of a sulfide solid-state lithium-sulfur battery. ADVANTAGE - The protective layer has high ion conductivity, low interface resistance, high ion conduction characteristics, and high capacity and cycle stability. The cathode is easy to obtain, raw material cost, and easy to expand, which is good for promoting industrial development of the solid battery. The interface protective layer is present between the sulphide solid electrolyte and the lithium metal cathode which can prevent the two directly contact occurring serious interface side reaction. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: preparation method of protective layer; and ulphide solid lithium sulphur battery using the interface protection layer.