Glass-ceramic solid electrolytes were prepared by crystallization of the mechanically milled 80Li(2)S(.)20P(2)S(5) glass and their electrical and electrochemical properties were examined. The glass-ceramics exhibited favorable features as a solid electrolyte for lithium secondary batteries such as high ambient temperature conductivity of 7.2 x 10(-4) S cm(-1), unity of lithium transport number, wide electrochemical window, and high stability, against lithium metal. All-solid-state cells In/80Li(2)S(.)20P(2)S(5) glass-ceramic/LiCoO2 worked as lithium secondary batteries at room temperature and maintained large discharge capacity of about 100 mA h g(-1) up to the 200th cycle with the charge-discharge efficiency of 100%. (C) 2004 Elsevier B.V. All rights reserved.