Highly ion-conductive Li6PS5X (X = Cl, Br, I) Li-argyrodites were prepared through a high-energy ball milling. Electrical and electrochemical properties were investigated. Ball-milled compounds exhibit a high conductivity between 2 and 7 x 10(-4) S/cm with an activation energy of 0.3-0.4 eV for conduction. These attractive properties were attributed to the spontaneous formation of crystallized Li-argyrodite during ball-milling. An optimization of milling time led to a conductivity of 1.33 x 10(-3) S/cm for the Li6PS5Cl phase with an electrochemical stability up to 7 V vs. lithium. An all solid state LiCoO2/Elec./ln lithium ion battery using ball-milled Li6PS5Cl as electrolyte was successfully assembled, and its room temperature performance is reported. (C) 2012 Elsevier B.V. All rights reserved.