Hemiammine lithium borohydride, LiBH4·1/2NH3, is characterized and a new Li+ conductivity mechanism is identified. It exhibits a Li+ conductivity of 7 × 10-4 S cm-1 at 40 °C in the solid state and 3.0 × 10-2 S cm-1 at 55 °C after melting. The molten state of LiBH4·1/2NH3 has a high viscosity and can be mechanically stabilized in nano-composites with inert metal oxides and other hydrides making it a promising battery electrolyte.