Computational search for dehydrogenation pathways and destabilization schemes in complex metal hydrides

First-principles modeling is rapidly emerging as a valuable tool in the search for new, high-density hydrides for use in mobile energy storage systems. These methods can be used to supplement experimental characterization techniques, and as a means to rapidly screen for new materials in order to guide subsequent experimental testing. We discuss how these characterization and materials-discovery capabilities have been used to explore the properties of two candidate hydrogen storage materials, Li₄BN₃H₁₀ and LiBH₄. For Li₄BN₃H₁₀, calorimetry experiments have been unable to definitively determine the thermodynamics of hydrogen release, as the dehydrogenation reaction occurs simultaneously with one or more additional reactions. By screening ∼20 candidate reactions, we have identified the likely dehydrogenation pathways, evaluated their thermodynamics, and assessed the potential for reversibility. Recent experiments have shown that H₂ desorption in LiBH4 can be facilitated by thermodynamic destabilization via mixing with MgH₂. We explore whether further destabilization is possible by evaluating desorption free energies for several other LiBH₄/metal-hydride combinations.