NOVELTY - Flexible solid electrolyte comprises: a first inorganic protective layer (11); an inorganic-organic composite electrolyte layer comprising an inorganic component and an organic component; and a second inorganic protective layer (14). The inorganic-organic composite electrolyte layer is disposed between the first inorganic protective layer and the second inorganic protective layer, where the inorganic component and the organic component collectively form a continuous ion conducting path.    USE - The flexible solid electrolyte is useful in an all-solid-state lithium battery (claimed), which is useful in a laptop computer, a smart phone, or an electric vehicle including plug-in hybrid electric vehicle or an electricity storage system.    ADVANTAGE - The flexible solid electrolyte: exhibits improved electrochemical stability, ionic conductivity and flexible characteristics and reduced interfacial resistance; provides the battery, which exhibits high thermal stability, and improved high-rate characteristics and energy efficiency; utilizes the inorganic-organic composite electrolyte layer, which exhibits improved ductility, and is free from defects including pin holes and cracks; and can be prepared by a method, which can be performed at room temperature.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an all-solid-state lithium battery, comprising: a cathode; an anode; and the flexible solid electrolyte disposed between the cathode and the anode; and    (2) preparing the flexible solid electrolyte, comprising: (a) spraying a first inorganic protective layer forming material on the cathode to form the first inorganic protective layer; (b) spraying an inorganic-organic composite electrolyte layer forming material on the first inorganic protective layer to form the inorganic-organic composite electrolyte layer; and (c) spraying a second inorganic protective layer forming material on the inorganic-organic composite electrolyte layer to form the second inorganic protective layer.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of the flexible solid electrolyte.    First inorganic protective layer (11)    Inorganic electrolyte (12)    Organic electrolyte (13)    Second inorganic protective layer (14)