Reversible hydrogen storage in LiBH₄ destabilized by milling with Al

Abstract

LiBH₄ possesses a high hydrogen content, and though it is highly stable, its restoration from LiH+B+H₂ can only be accomplished under unacceptable high temperature and pressure conditions (650 °C and 15 MPa). Recently, it has been reported that destabilizing LiBH₄ by, i.e., MgH₂, transition metal oxides and chlorides presents a promising approach to exert its potential for hydrogen storage. In the present study, we find that simple mechanical milling with Al in a mole ratio of 2:1, markedly improves the reversible dehydrogenation performance of LiBH₄. The system possesses a theoretical capacity of 8.5 wt. % and could be reversibly operated at 400–450 °C. The combined property and phase examinations suggest that the observed property improvement should be associated with the formation of AlB₂ in the dehydriding process. Further cyclic examination found that the system suffered from a serious capacity loss in the dehydriding/rehydriding cycles. A better understanding of the degradation mechanism may provide a means for further material property improvement.