Combined DFT and geometrical-topological analysis of Li-ion conductivity in complex hydrides

On the basis of DFT calculations, Li-ion migration was analyzed for LiBH4, LiNH2, Li2NH, Li2BH4NH2, Li4BH4(NH2)(3)and Li-5(BH4)(3)NH complex hydrides by means of the nudged elastic band method. In addition, a Voronoi-partition-based method, as implemented in the ToposPro program package, was adopted to determine cavities and channels in the complex hydrides and possible Li-ion migration pathways were computed. Experimental data for the Li-ion conductivity in the six compounds, measured by electrochemical impedance spectroscopy, have been taken from the literature and activation energies have been determined by a statistical analysis. A link between experimental and calculated activation energies has been evidenced, suggesting that topological analysis can provide good hints for the estimation of ion conductivity in complex hydrides.