Determination of the phase behavior of (LiNH2) c(LiBH4)1-c quaternary hydrides through in Situ X-ray diffraction

Jonathan Singer, Martin S. Meyer, Richard M. Speer, John E. Fischer, Frederick E. Pinkerton

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Solid hydride materials combining high gravimetric and volumetric hydrogen capacity, rapid hydrogenation and dehydrogenation kinetics, and low operating temperature are highly desirable for hydrogen storage on fuel cell vehicles. Recently, a material of nominal composition Li3BN2H 8, formed by combining LiNH2 and LiBH4 in a 2:1 ratio, has garnered much attention because of its high hydrogen release (up to 11.9 wt % hydrogen on heating above ̃200-250 °C). While the material is expected from previous experiments to exist in a single "Li 3BN2H8" α-phase, here it is shown that single-phase 2:1 Li3BN2H8 samples decompose with time into a combination of an R-phase composition enriched in LiNH2 compared to Li3BN2H8 and the 1:1 β-phase Li2BNH6. Through in situ X-ray diffraction of samples from the (LiNH2)c(LiBH 4)1-c system with c in the range 0.667-0.75 (corresponding to LiNH2:LiBH4 ) 2:1 to 3:1) prepared either by high-energy ball milling (HEBM) for 10 min (mixed) or HEBM for 300 min (milled), the equilibrium phase behavior of the quaternary α-phase was investigated. The complete equilibrium composition range of the α-phase at 50 °C was shown to be LiNH2:LiBH4 = ̃2.62:1-2.83:1 or c = 0.724-0.739. Also, an approximate phase diagram in the composition range c = 0.5-0.75 and temperature range T = 0-250 °C was generated.

Original languageEnglish (US)
Pages (from-to)18927-18934
Number of pages8
JournalJournal of Physical Chemistry C
Volume113
Issue number43
DOIs
Publication statusPublished - Nov 20 2009
Externally publishedYes

    Fingerprint

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this