Rehydrogenation and cycle studies of LiBH4–CaH2 composite

Rehydrogenation behavior of 6LiBH4 + CaH2 composite with NbF5 has been studied between 350 and 500 °C after dehydrogenation at 450 °C. The composite exhibits the best rehydrogenation feature at 450 °C in terms of the overall rehydrogenation rate and the amount of absorbed hydrogen. It is found that about 9 wt% hydrogen is absorbed at 450 °C for 12 h. Up to 10 dehydrogenation–hydrogenation cycles have been carried out for the composite. It is demonstrated that 6LiBH4 + CaH2 with 15 wt% NbF5 maintains a reversible hydrogen storage capacity of about 6 wt% at 450 °C after a slight degradation between the 1st and 5th cycles. The addition of NbF5 seems to improve the cycle properties by retarding microstructural coarsening during cycles.