Recent progress of glass and glass-ceramics as solid electrolytes for lithium secondary batteries

In recent years many new glass-based solid electrolytes with high Li⁺ conductivity have been developed. In the present paper, we review the preparation and characterization of Li₂S-based oxysulfide glasses and sulfide glass-ceramics on the basis of two strategies of enhancing Li⁺ conductivity: the utilization of “mixed-anion effect” by combining sulfide and oxide anions, and the precipitation of superionic metastable crystals by careful heat-treatment of glasses. The superior Li⁺ conducting solid electrolytes with the highest conductivity and the lowest activation energy for conduction have been achieved in the Li₂S–P₂S₅ glass-ceramics. The use of these glass-ceramic solid electrolytes leads to the development of a bulk-type all solid-state lithium secondary battery with excellent cycling performance.