Amorphous solid electrolytes in the ternary system Li2S-Al2S3-SiS2 were successfully prepared by mechanical milling. The ambient temperature conductivity of the 60Li(2)S.10AlS(1.5).30SiS(2) (mol%) sample reached over 10(-4) S cm(-1) with amorphization by mechanical milling for 40 h. The binary Li2S-Al2S3 amorphous electrolytes, which have not been synthesized by a conventional melt-quenching technique, were also obtained by mechanical milling. The 60Li(2)S.40AlS(1.5) (mol%) amorphous electrolyte exhibited lower conductivity and higher activation energy for conduction than the 60Li(2)S.40SiS(2) (mol%) amorphous electrolyte. The addition of SiS2 to Li2S-Al2S3 system monotonically increased electrical conductivity and decreased activation energy for conduction. The amorphous 60Li(2)S.10AlS(1.5).30SiS(2) material showed favorable features as a solid electrolyte such as unity of lithium ion transport number and wide electrochemical window. (C) 2004 Kluwer Academic Publishers.