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 + 3/2H2, occurring at 160 °C; (2) formation of an intermediate product from 300 °C to 350 °C, and then subsequent transformation into Al, AlB2, and H2. (2LiBH4 + Al → [Li2B2AlH4] → x(AlB2 + 2LiH + 3H2) + (1 − x) [Li2B2AlH4], (0 < x < 1)); and (3) final dehydrogenation of LiH + Al → LiAl + 1/2H2, occurring at 415 °C, with sequential decomposition of the remaining intermediate ((1 − x)[Li2B2AlH4]→(1 − x)(AlB2 + 2LiH + 3H2), (0 < x < 1)). Furthermore, the dehydrogenated products can be rehydrogenated to LiBH4 at 8 MPa H2 and 400 °C.

► A novel hydrogen storage system, LiBH4–Li3AlH6, was synthesized.
► The dehydrogenation/rehydrogenation mechanism of LiBH4–Li3AlH6 composite was studied.
► LiBH4–Li3AlH6 composite showed good hydrogen storage properties.