Li+ conductivity in the system Li2O-Nb2O5-P2O5-LiCl as solid electrolyte based on synthesized glasses and sintered glass ceramics

Abstract

All solid-state batteries (ASSB) employing solid Li-ion conductors instead of liquid electrolytes are considered promising candidates for future energy storage solutions with increased energy density and improved safety properties. For oxidic electrolytes, this is enabled by proper densification of the mixed powder compacts made of oxidic solid electrolyte and active material, e. g. by sintering at high temperatures. For this purpose, oxide glasses with lower softening temperatures (< 1000 °C) are discussed as Li-conductive electrolyte. Herein, the synthesis of Li-ion conductive glasses in the system Li2O-Nb2O5-P2O5-LiCl by means of melting and quenching, powder preparation by milling and sintering of powder compacts in air are investigated. The highest Li-ion conductivity of 5.5 × 10−6 S/cm was obtained for the optimized composition of 40Li2O-10Nb2O5-30P2O5-20LiCl in glassy state as well as for glass ceramics obtained after sintering at 700 °C. The high Li-ion conductivity of the glasses is retained in the glass-ceramic microstructure after sintering, although crystallization, grain size and porosity significantly influence the resulting overall properties.