Abstract
There are two types of solid electrolytes which has been recently expected to be applied to all-solid-state batteries. One is the glasses characterized by an amorphous state. The other is the glass ceramics containing crystalline in an amorphous matrix. However, the non-crystalline state of glasses and glass ceramics is still an open question. It has been anticipated that sea-island and core-shell structures including crystalline nanoparticles have been proposed as candidate models for glass ceramics. Nevertheless, no direct observation has been conducted so far. Here we report the non-crystalline state of Li2S–P2S5 glasses and glass ceramics, and the crystallization behavior of the glasses during heating via direct transmission electron microscopy (TEM) observation. High resolution TEM images clearly revealed the presence of crystalline nanoparticles in an amorphous region. Eventually we suggest that the precipitation and connection of crystalline nanoparticles in an amorphous matrix are key to achieving high ionic conductivity.
Highlights
Lithium-ion secondary batteries have received a lot of attention in recent years due to their excellent charge-discharge cycle characteristics and high energy density
We first examined the microstructure of the 80Li2S·20P2S5 glass ceramics obtained by heat-treatment at 240 °C
These nanoparticles appear to be LGPS analog crystals. This indicates that precipitation and connection of LGPS analog crystalline nanoparticles in an amorphous matrix contributes to a high ionic conductivity of more than 10−3 S cm−1 in the 80Li2S·20P2S5 glass-ceramics[10]
Summary
Lithium-ion secondary batteries have received a lot of attention in recent years due to their excellent charge-discharge cycle characteristics and high energy density. To resolve the safety problem, we focused on a sulfide-type all-solid-state battery using a non-flammable inorganic solid electrolyte. Li2S–P2S5 glass crystallizes by heat treatment, and its lithium ion conductivities highly depend on the type of precipitated crystalline phases and the composition of Li2S8, 9. Et al showed that conductivity was enhanced by crystallization with compositions from 70 to 85 mol% Li2S; the obtained glass-ceramics exhibited high conductivity of about 10−3 S cm−1 at room temperature. The high conductivities of Li2S–P2S5 glass-ceramics were directly associated with the percent composition of Li2S and the type of precipitated crystalline phase. Various experiments have been conducted so far to reveal the structure of Li2S–P2S5 solid electrolytes[13,14,15,16], there have been no direct observations of the microstructure of the corresponding glasses and glass ceramics. Provide the best experimental condition for in-situ TEM observation of Li2S–P2S5 solid electrolytes because the sulfide-based solid electrolyte is highly sensitive to electron beam irradiation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
