The electrical and electrochemical properties of the Li2S-P2S5-P2O5 glass-ceramic electrolytes were investigated. The 80Li(2)S. (20-X)P(2)S(5)(.)xP(2)O(5) (mol%) glass-ceramics were prepared by a mechanical milling and a subsequent heat treatment. The 80Li(2)S(.)19P(2)S(5) (.) 1P(2)O(5) glass-ceramic showed the high lithium ion conductivity of 7.4 x 10(-4) S cm(-1) at room temperature and the low activation energy of 34 U mol(-1) for conduction. The addition of a small amount of P2O5 to the Li2S-P2S5 sulfide system lowered the electronic conductivity and enhanced the electrochemical stability of the glass-ceramic electrolytes. All-solid-state In/LiCoO2 cells with the 80Li(2)S (.) 19P(2)S(5) (.) 1P(2)O(5) glass-ceramic as a solid electrolyte worked as lithium secondary batteries at room temperature. The cells maintained high discharge capacity of about 100 mAh g(-1) for 10 cycles. (c) 2005 Elsevier B.V All rights reserved.