The influence of phosphorous source on the properties of NASICON lithium-ion conductor Li1.3Al0.3Ti1.7(PO4)3

Abstract

Different sources of the starting materials can influence the properties of the lithium-ion conductors. Two different sources of phosphorous are used to prepare NASICON type lithium-ion conductor Li1.3Al0.3Ti1.7(PO4)3 via a hydrothermal-assisted solid-state method in this paper. X-ray diffraction (XRD), Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) are conducted to characterize the structure and morphology. Electrochemical impedance spectroscopy (EIS) is used to characterize the conductivity of the samples. The sample using NH4H2PO4 as phosphorus source exhibits a lower total conductivity than the sample using H3PO4 as phosphorus source, which is attributed to the lower relative density and the more porous microstructure obtained in N-LATP. While the more porous microstructure formed in N-LATP is rooted in the loss of driving force for sintering caused by the earlier crystallized rhombohedral phase LiTi2(PO4)3. The porous microstructure results in a tortuous path for lithium ions migration. Different sources of phosphorous can result in different reactions taken place in the hydrothermal reactor, thereby leading to a different particle size distribution, relative density, crystallography and morphology, eventually affecting the lithium ion conduction in the pelletized samples.