1. Field of the Invention
The present invention relates to a garnet-type ion conducting oxide, a complex, a lithium secondary battery, a manufacturing method of a garnet-type ion conducting oxide and a manufacturing method of a complex.
2. Description of the Related Art
Garget-type oxides such as Li7La3Zr2O12 and Li7ALa3Nb2O12 (A=Ca, Sr or Ba) synthesized by the solid-phase reaction method have been proposed conventionally as a solid electrolyte configured to conduct lithium ion (Non-Patent Literatures 1 to 3). It has been reported that this solid electrolyte has the conductivity of 1.9 to 2.3×10−4 Scm−1 (25° C.) and activation energy of 0.34 eV. The inventors have studied a solid electrolyte of Li7La3Zr2O12-based garnet-type ion conducting oxide among garnet-type oxides having excellent chemical stability and a wide potential window. For example, it has been proposed that the Zr sites in this solid electrolyte should be substituted with an element such as Nb, in order to enhance the conductivity (see, for example, Patent Literature 1). This solid electrolyte has high conductivity but needs treatment at high temperature such as 1200° C. It has been proposed, on the other hand, that La sites should be additionally substituted with an alkaline-earth metal, in order to minimize reduction of the electric conductivity and reduce the firing energy (see, for example, Patent Literature 2).
A solid electrolyte including Li, La, Zr, O and Al has been proposed as Li7La3Zr2O12-based solid electrolyte (see, for example, Patent Literature 3). According to the disclosure of this prior art, addition of Al to Li7La3Zr2O12-based solid electrolyte provides the solid electrolyte with the density and the conductivity required for the solid electrolyte material.