For the lithium super-ionic conductor Li10GeP2S12, the partial substitution of sulfur by oxygen is achieved via a solid-state reaction. The solid-solution range of oxygen is found to be 0 <= x < 0.9 in Li10GeP2S12-xOx. Structure refinements using synchrotron X-ray diffraction data confirm the preference for oxygen substitution in the PS4 tetrahedra. The local structural change in the P(S/O)(4) tetrahedra upon substitution is also indicated by Raman spectroscopy. Ionic conduction properties are maintained even after the oxygen substitution in Li10GeP2S12; the ionic conductivity of Li10GeP2S12-xOx (0.3 <= x <= 0.6) ranges from 1.03 x 10(-2) to 8.43 x 10(-3) S cm(-1) at 298 K. No redox current is observed by cyclic voltammetry from nearly 0 to 10 V versus Li/Li+ except for that due to the lithium deposition/dissolution reactions. All solid-state batteries using Li10GeP2S12-xOx (x = 0.3 and 0.6) as solid electrolytes with Li metal anodes show discharge capacities exceeding 100 mAh g(-1) and better cycling performance compared to batteries using the original Li10GeP2S12. The partial substitution of oxygen for sulfur in Li10GeP2S12 affords a novel solid electrolyte, Li10GeP2S12-xOx, with high conductive properties and electrochemical stability. (C) 2016 Elsevier B.V. All rights reserved.