Evaluation of a new lithium complex hydride: a derivative of BH4- and NH2- for fast Li-ion conduction and H2 sorption.

Abstract

A new ternary complex hydride is synthesized by the interaction between Li2NH and LiBH4. The crystal structure of this new hydride is tentatively indexed using an orthorhombic cell with a space group of Pna21 and lattice parameters of a = 9.643 Å, b = 6.228 Å, and c = 5.563 Å. The Li2NH-2LiBH4 sample shows excellent hydrogenation properties with hydrogen absorption starting at near-ambient temperature (50 °C), which is more than 100 °C lower than that of pristine Li2NH. Furthermore, it attains 100% hydrogenation under isothermal conditions at 60 °C and 50 bar hydrogen pressure. Such superior low-temperature hydrogen absorption may be due to the formation of this new complex hydride. Interestingly, above 97 °C, the lithium-ion conductivity of this new hydride is higher than those of Li2NH and LiBH4 and reaches 10-2 S cm-1 at 114 °C. Meanwhile, the ionic conductivity of this new hydride is ∼30 times higher than that of LiBH4 reaching 10-5 S cm-1 at room temperature. The interaction between imides and borohydrides described in this work expands the options for strategic design of novel hydrogen storage materials and solid ionic conductors.