Glass Electrolytes with High Ion Conductivity and High Chemical Stability in the System LiI-Li2O-Li2S-P2S5

The Li2O-Li2S-P2S5 glasses, which were prepared by a reaction of the Li2S-P2S5 glass and Li2O, hardly generated H2S gas in air. These glasses showed relatively high ion conductivities about 10(-4) S cm(-1) at room temperature. However, these conductivities were lower than those of original sulfide glasses. In this study, an addition of LiI to the Li2O-Li2S-P2S5 glasses was examined in order to improve ion conductivities. The 30LiI center dot 70(0.07Li(2)O center dot 0.68Li(2)S center dot 0.25P(2)S(5)) glass showed high ion conductivity of 1.3 x 10(-3) S cm(-1) at room temperature, and hardly generated H2S gas in air. On the other hand, the 30LiI center dot 70(0.07Li(2)O center dot 0.68Li(2)S center dot 0.25P(2)S(5)) glass was electrochemically stable in the potential range of 0-10V. Moreover, the all-solid-state C/LiCoO2 cell using the 30LiI center dot 70(0.07Li(2)O center dot 0.68Li(2)S center dot 0.25P(2)S(5)) glass as solid electrolytes worked as lithium secondary batteries at room temperature, and exhibited a good cycle performance. Therefore, the 30LiI center dot 70(0.07Li(2)O center dot 0.68Li(2)S center dot 0.25P(2)S(5)) glass was a suitable electrolyte for all-solid-state cells because the glass had high conductivity, wide electrochemical window and high chemical stability to moisture. (C) The Electrochemical Society of Japan, All rights reserved.