Solid electrolyte composition, solid electrolyte-containing sheet, all-solid state secondary battery, and methods for manufacturing solid electrolyte-containing sheet and all-solid state secondary battery

A solid electrolyte-containing sheet comprising:

• a layer containing (A) a sulfide-based inorganic solid electrolyte having a conductivity of an ion of a metal belonging to Group I or II of the periodic table, (B) an active material having a surface coated with an oxide having an ion conductivity, and a polar dispersion medium (C1) satisfying the following conditions 1 and 2,
• wherein a content of the polar dispersion medium (C1) in the layer is 1 ppm or more and 10,000 ppm or less,
• <condition 1>
• the polar dispersion medium has at least one polar group selected from the following group of polar groups,
• <group of polar groups>
• a hydroxy group, a sulfanyl group, an ether group, a sulfide group, an amino group, an amide group, an ester group, a carbonyl group, a carbonate group, a carboxy group, and a cyano group, and
• <condition 2>
• at least one of substituents that are bonded to the polar group is a hydrocarbon group having a branched structure.