Abstract: A composite of LiBH₄-Mg₂NiH₄ doped with 10wt% CeH_2.29 was prepared by ball milling followed by dynamic interspace vacuum treatment at 573 K. The introduction of CeH_2.29 caused a transformation in the morphology of Mg from complex spongy and lamellar to uniformly spongy, resulting in refined particle size and abundant H diffusion pathways. This LiBH₄-Mg₂NiH₄ + 10wt% CeH_2.29 composite exhibited excellent hydrogen storage properties. The starting temperature of rapid H absorption decreased to 375 K in the doped composite from 452 K for the unmodified material, and the onset decomposition temperature of its hydride was reduced from 536 K to 517 K. In addition, the time required for a hydrogen release of 1.5wt% (at 598 K) was 87 s less than that of the un-doped composite.