Preparation of the Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte with high ionic conductivity

A new effective method is proposed for synthesis of the Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 powdered solid electrolyte of NASICON structure with high lithium ionic conductivity. The advantage of the method consists in use of a liquid-phase precursor based on the water-soluble Ge(IV) oxalate complex. Chemical interaction in a multicomponent solution containing a liquid-phase precursor results in a target product without the formation of intermediate compounds. This makes it possible to diminish considerably the synthesis temperature (to 650°C) and duration of preparation of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 powders owing to a better homogenization of the reaction mixture and also to simplify the technological operations. The synthesized Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 powders are studied by the XRD, DSC/TG, and IR spectroscopy methods, as well as by chemical analysis, SEM, and impedance spectroscopy. The conditions are determined for production of polycrystalline Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 solid electrolyte with the maximum bulk ionic conductivity of 1 × 10 –3 S/cm at room temperature.