Heat and gas transport properties in pelletized hydride–graphite-composites for hydrogen storage applications

Metal hydrides are suitable for the compact, efficient and safe storage of hydrogen. Considering hydride-based hydrogen storage tanks, the enhancement of the heat and gas transport properties of the hydride bed is crucial for increased (un-)loading dynamics of the tank.In this contribution, pelletized composites of different hydrogen storage materials (lithium amide, sodium alanate, magnesium hydride and transition metal hydride Hydralloy C5) with expanded natural graphite (ENG) are discussed. The materials were admixed with up to 25 wt.% ENG and compacted at compaction pressures up to 600 MPa. The resulting hydride-ENG pellets exhibit an increased effective thermal conductivity which can be tuned in a wide range. The pellets have an increased volumetric H2 storage capacity compared to loose hydride powders. High gas permeability in radial direction and sufficient thermal conductivity (>10 W m−1 K−1) in combination with a stable pellet structure indicate a high potential to use suchlike prepared hydride-ENG composites for hydrogen storage applications with high loading dynamics.

► Pelletized Hydride–Graphite composites were prepared. ► Increased hydrogen storage capacities compared to loose powders were obtained. ► A wide range of thermal conductivity and residual porosity can be adjusted. ► High gas permeability in radial direction throughout cyclic hydrogenation were achieved. ► Hydride–Graphite pellets remain stable during hydrogenation–dehydrogenation cycling.