Solid state lithium secondary batteries using an amorphous solid electrolyte in the system (100−x)(0.6Li2S·0.4SiS2)·xLi4SiO4 obtained by mechanochemical synthesis

Electrochemical cells were constructed using amorphous materials in the system (100−x)(0.6Li2S·0.4SiS2)·xLi4SiO4, obtained by mechanochemical synthesis, as an electrolyte, LiCoO2 as a positive electrode and indium as a negative electrode. Charge and discharge behaviors of the cells at a constant current were investigated to see the possibility for utilization as secondary batteries. Charge–discharge efficiency at the 1st cycle was more than 75% in the cells using the solid electrolytes synthesized by mechanical milling (MM) for more than 5 h. Charge–discharge curves of the cells using the amorphous materials milled for more than 10 h, were similar to those of the cells using the corresponding melt-quenched glass samples. The charge–discharge capacity decreased gradually from 90 to 70 mA h/g till about the 10th cycle, and became stable after the 10th cycle. The Coulombic efficiency of the cell showed almost 100%, except for the 1st and 2nd cycles. The amorphous materials synthesized by MM were concluded to work as the electrolyte for solid state lithium secondary batteries.