Lithium-ion Conductors Prepared by Low-temperature Heat Treatment of Amorphous Materials with the Composition of High-Al Substituted Li<sub>1+</sub><i><sub>x</sub></i>Al<i><sub>x</sub></i>Ge

Amorphous powder with the composition of high-Al substituted Li1+xAlxGe2−x(PO4)3 (x = 1.0) [LAGP(x = 1.0)] were prepared by mechanical milling treatment of the starting materials. Crystalline compounds with LiGe2(PO4)3-based NASICON-type structure were mainly formed by low-temperature heat treatment of amorphous LAGP(x = 1.0) at 450–750 °C. NASICON-type solid electrolytes prepared by the heat treatment of pelletized-type amorphous LAGP(x = 1.0) at 600–750 °C exhibited relatively high conductivities on the order of 10−5 S cm−1 at room temperature, although they contained AlPO4 and Li9Al3(P2O7)3(PO4)2 compounds. The LAGP-type high-Al solid electrolytes would be a potential candidate as lithium-ion conductors for all-solid-state battery applications.