Influence of phosphorus sources on lithium ion conducting performance in the system of Li2O–Al2O3–GeO2–P2O5 glass–ceramics

• The effect of phosphorus sources on LAGP glass–ceramics' conductivities is studied.
• Highly pure NASICON phase is prepared when H3PO4 is used as a phosphorus source.
• The highest conductivity is obtained with H3PO4 as a phosphorus source.

NASICON-type structure lithium ion conductors have been considered as promising solid electrolytes due to its very high Li+-ion conductivity and chemical stability. In this paper, NASICON-type structured Li1.5Al0.5Ge1.5(PO4)3 (LAGP) glass–ceramics are prepared from crystallization of glass powders, which are obtained by a simple melt-quench method. NH4H2PO4, H3PO4, P2O5 and H3PO4&Al(PO3)3 are used as phosphorus sources, respectively. The obtained LAGP glass–ceramics are systematically characterized with X-ray diffraction, field emission scanning electron microscopy, differential scanning calorimetry and AC impedance spectroscopy. The different impurities are formed depending on the phosphorus sources, which further influence the microstructure. As a result, the lithium ion conductivity is significantly affected by the phosphorus sources. The highest conductivity of 5.21 × 10− 4 S·cm− 1 is obtained when H3PO4 is used as the phosphorus source under optimum conditions.