Preparation and ionic conduction of Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte using inorganic germanium as precursor

NASION-type Li1.5Al0.5Ge1.5(PO4)3(LAGP) is prepared by a novel sol-gel method using low cost inorganic germanium (GeO2) as the precursor. The composition and phase transformation during the heating of the LAGP precursors are analyzed using thermogravimetric-differential scanning calorimetry (TG-DSC) and X-ray diffraction (XRD). The structures and morphologies of the LAGP are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the LAGP annealed at 900 ℃ is partially crystallized and consists of a large number of nanoscale grains surrounded by amorphous regions. The LAGP particles present an irregular morphology with a large size distribution over a range of 0.2–1 μm. In addition, ionic conductivities of the prepared LAGP first increase and then decrease with an increase in the sintering temperature and time. A high ionic conductivity (4.18 × 10−4Scm-1) with an activation energy of 0.30 eV are obtained for the LAGP sample sintered at 900 °C for 8 h.