(100 − x)(0.75Li2S·0.25P2S5)·xLiBH4 (0 ≤ x (mol%) ≤ 33) glass electrolytes were prepared from 75Li2S·25P2S5 (mol%) glass and LiBH4 crystal by a mechanical milling technique. The effects of the addition of LiBH4 on the structures and properties of the glass electrolytes were examined. The DSC curves of the prepared glasses with LiBH4 did not have the endothermic peak attributable to the phase transition of LiBH4 crystal. The Raman spectra of the glasses indicated that the glasses included PS4 3− and BH4 − ions. The conductivities of the glasses increased with increasing the LiBH4 content. The glass at the composition of x = 33 showed the highest lithium-ion conductivity of 1.6 × 10−3 S cm−1 at room temperature. The glass had a wide electrochemical window up to 5 V vs. Li+/Li. An all-solid-state Li/TiS2 cell using the glass as an electrolyte successfully operated as a secondary battery at 25 °C.