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Solid-state hydrogen storage in Hydralloy-graphite composites

: Pohlmann, C.; Röntzsch, L.; Heubner, F.; Weissgärber, T.; Kieback, B.


Journal of power sources 231 (2013), pp.97-105
ISSN: 0378-7753
Bundesministerium für Bildung und Forschung BMBF
Journal Article
Fraunhofer IFAM, Institutsteil Pulvermetallurgie und Verbundwerkstoffe Dresden ()

Hydrogen-based power systems require safe, efficient and robust hydrogen storage solutions. In this regard, metal hydrides become increasingly important because of their extremely high volumetric hydrogen capacity and their moderate operation pressures. The loading and unloading dynamics of hydride-based hydrogen tanks is mainly influenced by the intrinsic hydrogen sorption kinetics of the storage material as well as by the heat and gas transport properties of the hydride bed. In this contribution, pelletized composites of the room-temperature hydrogen storage material Hydralloy C5(2) (AB(2)-type) with expanded natural graphite (ENG) are discussed in view of high-dynamic hydrogen solid-state storage applications. Powdery Hydralloy C5(2) is blended with up to 12.5 wt.% ENG. The blend is pelletized at compaction pressures up to 600 MPa. The Hydralloy ENG pellets exhibit an increased effective thermal conductivity and provide an increased volumetric H-2 storage capacity compared to loose powders. The hydrogenation behavior at different temperatures and for various hydrogenation dehydrogenation cycles is discussed. Furthermore, the stability of the pellets throughout cyclic hydrogenation is evaluated. High gas permeability in radial direction and sufficient thermal conductivity in combination with a stable pellet structure underline the potential of Hydralloy ENG composites for hydrogen storage applications with high loading dynamics.