Abstract: A solid electrolyte contains a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and an X element, where X represents at least one element selected from the group consisting of a chlorine (Cl) element, a bromine (Br) element, and an iodine (I) element. The solid electrolyte has a peak attributed to a fluorine (F) element in surface analysis based on X-ray photoelectron spectroscopy. It is preferable that the ratio (quantitative value of F1s/quantitative value of P2p) of quantitative value of F1s (atom %) and quantitative value of P2p (atom %), calculated based on X-ray photoelectron spectroscopy with the total amount of Li1s, C1s, O1s, F1s, P2p, S2p, Cl2p, and Br3d being set to 100%, is 0.01 or more and 0.34 or less.

Abstract: A method for producing a sulfide solid electrolyte includes: a step of mixing a lithium (Li) element source, a phosphorus (P) element source, and a sulfur (S) element source, thereby obtaining a raw material composition; a step of firing the raw material composition, thereby obtaining a sulfide; a step of milling a slurry containing a solvent having fluorine atoms and the sulfide; and a step of drying the slurry. The sulfide in the slurry preferably has a concentration of 3 to 40 mass %. The step of milling a slurry is preferably a step of dry milling the sulfide, and mixing the dry milled sulfide and the solvent, thereby preparing the slurry.

Abstract: A sulfide solid electrolyte having ionic conductivity is provided. The sulfide solid electrolyte contains an organic solvent. The amount of organic solvent contained in the sulfide solid electrolyte is 0.95 mass % or less. It is preferable that the amount of organic solvent contained in the sulfide solid electrolyte is 0.01 mass % or more. It is preferable that the sulfide solid electrolyte has an argyrodite-type crystal structure. Also provided are an electrode mixture including the sulfide solid electrolyte and a positive electrode active material or a negative electrode active material, as well as a solid-state battery including the electrode mixture.