Grain boundary resistance of fast lithium ion conductors: Comparison between a lithium-ion conductive Li–Al–Ti–P–O-type glass ceramic and a Li1.5Al0.5Ge1.5P3O12 ceramic

The structure and ionic conductivity of a lithium-ion conductive Li–Al–Ti–P–O-type glass ceramic (LATP) was studied by means of powder X-ray diffraction, transmission electron microscopy, and broadband impedance spectroscopy. The results were compared to a Li1.5Al0.5Ge1.5P3O12 (LAGP) ceramic. While the grain conductivity of LATP is higher than that of LAGP, the total conductivity of LATP is lower due to a large grain boundary resistance. The grain boundary resistance of LATP is characterized by a slightly higher activation energy and a slightly higher pre-exponential factor than the grain resistance. Our results indicate that the origin of the grain boundary resistance in these fast lithium ion conductors is clearly distinct from oxide ion conductors.

► Grain and grain boundary resistance of Li-Al-Ti-P-O (LATP) glass-ceramic was investigated in detail.
► Grain conductivity of the LATP is higher than that of Li1.5Al0.5Ge1.5P3O12 ceramic.
► Total conductivity of the LATP is lower due to a large grain boundary (gb) resistance.
► Results show the origin of gb resistance in these fast lithium ion conductors is clearly distinct from oxide ion conductors.