Lithium Ion Conductivities of Solid Electrolytes Prepared by Low-temperature Heat Treatment of Amorphous Materials in the Li2O-Al2O3-GeO2-P2O5 System for All-solid-state Batteries

Amorphous materials (a-LAGP(x = 0.5)) with the composition of Li1.5Al0.5Ge1.5(PO4)3 were prepared by mechanochemical synthesis method. Crystalline compounds with LiGe2(PO4)3-based NASICON-type structure were formed by heat treatment of a-LAGP(x = 0.5) at 400–700 °C in air. Solid electrolytes prepared by the heat treatment of pelletized-type a-LAGP(x = 0.5) and MgO-modified a-LAGP(x = 0.5) at 700 °C exhibited the lithium ion conductivities on the order of 10−5–10−4 S cm−1 at room temperature. The addition of MgO into a-LAGP(x = 0.5) increased the electrical conductivity. Lithium ion conductors prepared by low-temperature heat treatment of pelletized-type amorphous materials in the Li2O-Al2O3-GeO2-P2O5 system would be promising as solid electrolytes for all-solid-state batteries.