SOLID ELECTROLYTE, METHOD OF PREPARING THE SAME, LITHIUM-AIR BATTERY INCLUDING THE SOLID ELECTROLYTE, AND ELECTROCHEMICAL DEVICE INCLUDING THE SOLID ELECTROLYTE

A solid electrolyte includes a first layer including an inorganic lithium-ion conductor, and a second layer disposed on at least one surface of the first layer, wherein the second layer includes at least one of a compound represented by Formula 1 or a compound represented by Formula 2: LiMO Formula 1 LiM(OH) Formula 2 wherein, in Formulae 1 and 2, each M is independently at least one of a monovalent element to a hexavalent element, and each of x, y, and z are independently 0