Hydrogen absorption and lithium ion conductivity in Li₆NBr₃

The reaction of lithium amide and imide with lithium halides to form new amide halide or imide halide phases has led to improved hydrogen desorption and absorption properties and, for the amides, lithium ion conductivities. Here we investigate the effect of bromide incorporation on the ionic conductivity and hydrogen absorption properties of lithium nitride. For the first time we show that it is possible for a lithium halide nitride, the cubic bromide nitride Li₆NBr₃, to take up hydrogen—a necessary condition for potential use as a reversible solid-state hydrogen storage material. Powder X-ray diffraction showed the formation of Li₂Br(NH₂) and LiBr, and Raman spectroscopy confirmed that only amide anions were present and that the hydrogen uptake reaction had gone to completion. The lithium ion conductivity of Li₆NBr₃ at the hydrogenation temperature was found to be less than that of Li₃N, which may be a significant factor in the kinetics of the hydrogenation process.