SOLID ELECTROLYTE LAYER AND ALL-SOLID-STATE SECONDARY BATTERY

A solid electrolyte layer includes a first phase region containing a first solid electrolyte which contains Li, Si, P and O and has a γ-LiPOtype crystal structure, and a second phase region containing a second solid electrolyte which contains Li, Si, P and O, has a different composition from the first solid electrolyte, and has a LiSiOtype crystal structure. In the solid electrolyte layer, the ratio of the volume of the first phase region to the volume of the second phase region is preferably 0.1 or more and 9 or less.