Thermal evolution of NASICON type solid-state electrolytes with lithium at high temperature via in situ scanning electron microscopy.

We present the thermal evolution of two NASICON-type ceramics namely LATP (Li1+xAlxTi2-x(PO4)3) and LAGP (Li1+xAlxGe2-x(PO4)3) by monitoring the electrode-electrolyte interfaces (i.e., Li/LATP and Li/LAGP) at temperatures up to 330 °C via in situ scanning electron microscopy, post-mortem energy-dispersive spectroscopy, and X-ray diffraction. Upon melting of Li and contacting electrolytes, LAGP decomposes completely to form Li based alloys, while LATP is partially decomposed without alloying.