(403d) Scaled up LiBH4 - MgH2 Composite Storage System as New Promising Hydrogen Storage

The discovery of the reaction mechanism of the Reactive Hydride Composite (RHC) some years ago, where the reaction of two metal hydrides lowers the overall reaction enthalpy [1, 2] gave new impetus to the entire hydrogen storage technology. RHCs combine high hydrogen storage capacities and relatively fast sorption rates, but at more moderate temperature and pressure conditions compared to the conventional high pressure (up to 700 bar) and liquid (-253 °C) storage systems. In particular for the promising combination of LiBH4 and MgH2 many investigations were done for a deep understanding of the reaction pathways (e.g. [3]). However, a scaled up tank system containing the LiBH4-MgH2 composite had not been investigated until now. In this paper we present the first results of such a system concerning the storage capacity, sorption rates and cycling behaviour. The investigated maximum temperature and hydrogen pressure conditions are at 400 °C and 50 bar respectively. The inner tank volume is 600 cm3. The theoretical investigation is performed by calculation of the mass and energy balances. Besides the use of a fluid heat transfer medium we also investigate the possibility of a electrical heat management. Hence we achieve further considerable weight and volume savings. However, the main advantage is the possibility of a free form tank system due to a flexible heat management and the maximum pressure of 50 bar. A free form tank system is advantageous for the automotive industry and most other mobile and stationary applications and can be considered as breakthrough in the hydrogen storage technology for high temperature hydrides.

References [1] Barkhordarian, G., Klassen, T., Dornheim, M., Bormann, R., 2007. Unexpected kinetic effect of MgB2 in reactive hydride composites containing complex borohydrides. Journal of Alloys and Compounds 440, L18-L21. [2] Vajo, J.J., Skeith, S.L., Mertens, F., 2005. Reversible Storage of Hydrogen in Destabilized LiBH4. J. Phys. Chem. B 109, 3719-3722. [3] Bösenberg, U., Doppiu, S., Mosegaard, L., Barkhordarian, G., Eigen, N., Borgschulte, A., Jensen, T.R., Cerenius, Y., Gutfleisch, O., Klassen, T., Dornheim, M., Bormann, R., 2007. Hydrogen sorption properties of MgH2-LiBH4 composites. Acta Materialia 55, 3951-3958.