Hydrogen storage properties of modified lithium borohydrides

This paper reports the results of using various metal oxides and metal chlorides as additives to modify lithium borohydride for reversible hydrogen storage. Two approaches - element substitution and additive interaction - were attempted for reducing dehydriding temperatures and improving dehydriding-rehydriding reversibility. The oxide-modified borohydride, LiBH4 75% + TiO2 25%, desorbed 9 wt% hydrogen from 100 °C to 600 °C and absorbed 8 wt% hydrogen at 600 °C and 70 bar. The chloride-modified borohydride, LiBH4 + 0.2MgCl2 + 0.1TiCl3, desorbed 5 wt% hydrogen from 60 °C to 450 °C and absorbed 4.5 wt% hydrogen at 600 °C and 70 bar. XRD analysis evidences that LiBH4 reacts with the additives. The residual gas analyzer (RGA) spectra show no diborane evolved from the above materials during dehydrogenation. The reduction of desorption temperature can be attributed to additives interaction with lithium borohydrides rather than element substitution. The reversibility of oxide-modified LiBH4 deteriorates during repeatedly dehydriding-rehydriding due to increasing formation of Li3BO3 and sequent deficiency of boron and lithium.