Preparation and characterization of glassy materials for all-solid-state lithium secondary batteries

Glass is an attractive material as a solid electrolyte and an electrode for all-solid-state lithium secondary batteries. In the present paper, the preparation and characterization of Li2S-based oxysulfide glasses and sulfide glass-ceramics as solid electrolytes are reviewed. In particular, two strategies of enhancing Li+ conductivity are proposed; one strategy is the utilization of "mixed-anion effect" by combining sulfide and oxide anions (in oxysulfide systems) and the other is 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. For the SnO-based glasses as a negative electrode in a lithium ion cell, the relationship between electrochemical performance and local structure is also discussed. All-ceramic electrochemical cells using the oxysulfide glassy electrolytes and the SnO-B2O3 glassy electrodes were fabricated and then characterized as a lithium secondary battery.