Experiment and simulations are used to investigate the structural and electrolyte properties of Li4P2S6. Compared with other thiophosphate materials, Li4P2S6 is quite stable, maintaining its crystal structure up to temperatures as high as 950 degrees C in vacuum and up to 280 degrees C in air. While its ionic conductivity is small, 2.38 x 10(-7) S/cm at 25 degrees C and 2.33 x 10(-6)S/cm at 100 degrees C, its Arrhenius activation energy of 0.29 eV is similar to technologically viable electrolytes. Computer simulations provide insight into the causes and effects of disorder in this material and also indicate that the mechanism of the ion conduction is dominated by interstitial sites. (C) 2015 Elsevier B.V. All rights reserved.