Mechanochemical Synthesis of the High Lithium lon Conductive Amorphous Materials in the Systems Li2S-SiS2 and Li2S-SiS2-Li4SiO4.

Abstract

Amorphous materials in the system xLi₂S⋅(100-x)SiS₂, where x ranged from 50 to 70mol%, and (100-y)(0.6Li₂S⋅0.4SiS₂)⋅yLi₄SiO₄, where y ranged from 0 to 10mol%, were synthesized by mechanical milling of crystalline starting materials, Li₂S, SiS₂ and Li₄SiO₄. At the compositions with large amounts of Li⁺ ions, a part of crystalline Li₂S used as a starting material remained in the milled powder samples. It was found that the milled powder samples in both systems obtained by mechanical milling exhibited high conductivities in the order of 10^-4S·cm^-1 at room temperature in spite of the presence of small amounts of Li₂S crystals. The conductivity values of the pelletized samples of xLi₂S⋅(100-x)SiS₂ powders maximized at the composition of about x=60. On the other hand, the conductivities in the composition range with y≤5 in the system (100-y)(0.6Li₂S⋅0.4SiS₂)⋅yLi₄SiO₄ were nearly the same values in the measured temperature range and higher by a half order of magnitude than those at the composition with y=10. The transport number of lithium ions of the amorphous materials after mechanically milled was almost unity and the potential window was wider than 10V at room temperature.