Structural Analysis of Sulfide-Based Crystallized Glass Solid Electrolyte by TEM

In the Li2S-P2S5 glass electrolyte systems, the ionic conductivity strongly depends on both the type of precipitated crystalline phases and heat treatment conditions. In order to clarify thermal behavior of the ionic conductivity, we have investigated the crystallization behavior as a function of the temperature by in-situ transmission electron microscopy (TEM) observation. In-situ TEM observation reveals that the crystallization process is mainly characterized by the formation of β-Li3PS4 nanocrystallites precipitated above 180 °C, whose size remains unchanged during further heating until 250 °C. That is, the increase in the density of β-Li3PS4 nanocrystals within the amorphous matrix attributed dominantly to the crystallization behavior. The present experimental results suggested that the formation processes of the β-Li3PS4 nanocrystals in the amorphous matrix should play the crucial role for better understanding of the thermal behavior of the ionic conductivity of 75Li2S-25P2S5 glass.