Solid state electrolytic properties of mixtures of Li(BH4)(0.75)I-0.25 and amorphous 0.75Li(2)S center dot 0.25P(2)S(5) are reported in this study. The enhanced Li-ion conductivities for the Li(BH4)(0.75)I-0.25 phase after addition of 0.75Li(2)S center dot 0.25P(2)S(5) were found to be within the range for practical solid-state electrochemical storage near room temperature. The highest ionic conductivities are found for the borohydride/sulfide system at 1: 2 wt ratio with similar to 10(-3) S cm(-1) at room temperature and an activation energy of 0.30(2) eV. Combined experimental analyses with powder X-ray diffraction and infrared spectroscopy suggest that the synthesized material still include both [PS43-] and [BH4-] entities. Density functional theory (DFT) calculations provide more insights about the origin of the observed ionic behavior according to the induced structural modifications in the BH4-BH4 interactions. Finally, the electrolyte functionality and its compatibility toward an active material are successfully demonstrated by means of cyclic voltammetry (Au vs. Lithorn/Li) in a large voltage window (up to 5 V) and battery cycling tests with TiS2 electrode, respectively. (C) 2018 Elsevier Ltd. All rights reserved.