▎ 摘　　要

NOVELTY - A composite solid electrolyte layer comprises a solid electrolyte layer (A) including gallium-doped lithium lanthanum zirconium oxide, and a solid electrolyte layer (B) provided on the layer (A) and containing aluminum-doped lithium lanthanum zirconium oxide. USE - Composite solid electrolyte layer for manufacture of all-solid lithium secondary battery (all claimed). ADVANTAGE - The electrolyte has controlled reactivity with lithium, and provides secondary battery having high discharge capacity. DETAILED DESCRIPTION - A composite solid electrolyte layer comprises a solid electrolyte layer (A) including gallium-doped lithium lanthanum zirconium oxide of formula: LixGaqLayZrzO12, and a solid electrolyte layer (B) provided on the layer (A) and containing aluminum-doped lithium lanthanum zirconium oxide of formula: LixAlpLayZrzO12, where x is 5-9, p,q are 0-4, and q is preferably 0.1-0.5, y is 2-4, and z is 1-3. INDEPENDENT CLAIMS are included for the following: (1) all-solid lithium secondary battery; and (2) manufacture of all-solid lithium secondary battery.