Lithium borohydride and substitutional derivatives with other compounds, such as LiI and LiNH₂, are attractive due to their promising properties for hydrogen storage. Recently, it has been reported that they exhibit super ionic conductivity toward lithium ion, which makes them attractive candidates for solid electrolytes in all-solid-state Lithium Ion Batteries (LIBs). In this study, LiBH₄ - LiNH₂ and LiNH₂-LiI mixed compounds have been synthesized by mechanical ball milling. Their ionic conductivities have been studied. Their thermal stabilities and chemical stabilities (towards Li metal and C) are analyzed by DSC measurement. Full cells are built with graphite as positive electrode and Li as contra electrode and LiBH₄, LiBH₄ - LiNH₂ and LiNH₂-LiI as solid electrolyte. Their electrochemical stabilities are studied by cyclic voltammetry. This research provides deeper understanding for LiBH₄-LiNH₂-LiI ternary system and the possibility as solid electrolyte for all-solid-state LIBs.