AbstractLiF−MgB2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH4, a significantly kinetic destabilization regarding hydrogenation and dehydrogenation is accomplished. The reversible hydrogen storage capacity is up to 6.4 wt %. The kinetic properties are improved significantly during cycling. The formations of the hydridofluoride phases (LiBH4−yFy and LiH1−xFx) are observed by in situ synchrotron X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Hydrogenation and dehydrogenation mechanisms are described on the basis of the formation and decomposition of the hydridofluoride phases, respectively.