부산대학교 도서관

Provided is a lithium ion conductive composite electrolyte that can prevent leakage of electrolyte solution, and that have excellent cycle performance and lithium ion conductivity, and a lithium ion secondary battery. A lithium ion conductive composite electrolyte 1 is formed so that a lithium ion conductive polymer gel electrolyte is held in a porous body 2 formed from lithium ion conductive inorganic solid electrolyte particles and an organic polymer. The lithium ion conductive inorganic solid electrolyte particles are formed from a composite metal oxide that has a garnet structure, and is represented by the chemical formula Li7−yLa3−xAxZr2−yMyO12 (wherein 0≦x≦3, 0≦y ≦2, A is one of Y, Nd, Sm, and Gd, and M is Nb or Ta). A lithium ion secondary battery 11 includes the lithium ion conductive composite electrolyte 1 between a positive electrode 12 and a negative electrode 13.