Hydrogen storage properties of LiBH4-Li3AlH6 composites

To improve the dehydrogenation properties of LiBH4, a novel hydrogen storage system, LiBH4-Li3AlH6, was synthesized by mechanical ball milling. The dehydrogenation/rehydrogenation properties of LiBH4-Li3AlH6 (molar rato: 1: 1) composites were studied via thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectral analysis (MS), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The experimental results show that the hydrogen desorption capacity reaches 8.5 wt% and that the whole dehydrogenation is a three-step process: (1) a decomposition reaction Li3AlH6 -> 3LiH + Al + 3/2H(2), occurring at 160 degrees C; (2) formation of an intermediate product from 300 degrees C to 350 degrees C, and then subsequent transformation into Al, AlB2, and H-2. (2LiBH(4) + Al -> [Li2B2AlH4] -> x(AlB2 + 2LiH + 3H(2)) + (1-x) [Li2B2AlH4], (0 < x < 1)); and (3) final dehydrogenation of LiH + Al -> LiAl + 1/2H(2), occurring at 415 degrees C, with sequential decomposition of the remaining intermediate ((1-x)[Li2B2AlH4]->(1-x)(AlB2 + 2LiH + 3H(2)), (0 < x < 1)). Furthermore, the dehydrogenated products can be rehydrogenated to LiBH4 at 8 MPa H-2 and 400 degrees C. (C) 2011 Elsevier B. V. All rights reserved.