There is much interest in developing new energy storage systems to replace currently available ones that mainly work based on Li-ion intercalations. One attractive area is the Li-air battery for which most of the research has involved liquid electrolytes. There have been few studies on the use of a solid electrolyte in a Li-air battery. Recently, we reported the successful use of a solid-state electrolyte in a Li-air battery resulting in a Li2O product and potentially much higher energy density than in a Li-air battery based on either a Li2O2 or LiO2 product (Science, 2023, 379, 499). In this paper we discuss how the discharge mechanism involved in this solid-state Li-air battery differs from that of a Li-air battery with a liquid electrolyte. The solid-state mechanism is further explored with density functional studies of various interfaces involving the discharge product. We discuss the relevance of the results to the discharge mechanism in the solid-state Li-air battery.