All-solid-state lithium secondary batteries using Li2S–SiS2–Li4SiO4 glasses and Li2S–P2S5 glass ceramics as solid electrolytes

Highly lithium ion conducting Li2S–SiS2–Li4SiO4 glasses and Li2S–P2S5 glass ceramics were prepared by using the melt-quenching method and the mechanical milling method, respectively. All-solid-state In/LiCoO2 cells using the glass and glass ceramic as solid electrolytes were assembled and their cell performances were evaluated at room temperature. Although the cells worked as lithium secondary batteries, they had large irreversible capacities at the 1st cycle. Cyclic voltammetry (CV) suggested that an irreversible anodic reaction occurred only at the 1st cycle in both cells. By using charge–discharge conditions optimized, the solid-state cells with Li2S–SiS2–Li4SiO4 glasses and Li2S–P2S5 glass ceramics respectively kept high discharge capacity around 60 and 100 mA h g−1 over 100 cycles with charge–discharge efficiencies around 100%.