Effect of the structural evolution on the ionic conductivity of Li-N-H system during the dehydrogenation.

On the way to transform lithium amide (LiNH2) into lithium imide (Li2NH) by releasing H2, the 1:1 molar mixture of LiNH2-LiH forms cubic (Fm3m)Fm3m) non-stoichiometric complex hydride phases (Li1+xNH2-x; 0<x<1) that co-exist with the tetragonal (I4)(I4) LiNH2 and with the cubic (Fd3m)Fd3m) Li2NH, respectively, at the early and at the advanced stage of the dehydrogenation. The change in LiNH2→Li2NH may be viewed as a mechanism which continuously fills up the vacant Li sites of the tetragonal structure and, in a parallel process, transforms the anions [NH2]-→[NH]2-. The Li-N-H system, thus formed, by releasing >6wt.% H2 can offer high Li-ionic conductivity (>10-4 S.cm-1 at room temperature) having an electrochemical stability window >5V. The study suggests that the Li-N-H system may be a prospective electrolyte in the all-solid-state Li-ion battery, in addition to its use as a reversible hydrogen storage material. [ABSTRACT FROM AUTHOR]