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• A novel waxberry-like Fe 3 O 4 (w -Fe 3 O 4) is developed as multifunctional additive. • The w -Fe 3 O 4 strongly destabilized LiBH 4 , leading to dehydrogenation below 100 °C. • In situ formed FeB/Fe 2 B as catalytic nucleation sites for (de)hydrogenation of LiBH 4. • A capacity retention of 70% is achieved after 10 cycles for LiBH 4 with 30wt% w -Fe 3 O 4. • The bidirectional catalytic mechanism of FeB/Fe 2 B as e− transfer medium is revealed. LiBH 4 containing 18.5 wt.% H 2 is an attractive high-capacity hydrogen storage material, however, it suffers from high operation temperature and poor reversibility. Herein, a novel and low-cost bifunctional additive, waxberry-like Fe 3 O 4 secondary nanospheres assembled from ultrafine primary Fe 3 O 4 nanoparticles, is synthesized, which exhibits significant destabilization and bidirectional catalyzation towards (de)hydrogenation of LiBH 4. With an optimized addition of 30 wt.% waxberry-like Fe 3 O 4 , the system initiated dehydrogenation below 100 °C and released a total of 8.1 wt.% H 2 to 400 °C. After 10 cycles, a capacity retention of 70% was achieved, greatly superior to previously reported oxides-modified systems. The destabilizing and catalyzing mechanisms of waxberry-like Fe 3 O 4 on LiBH 4 were systematically analyzed by phase and microstructural evolutions during dehydrogenation and hydrogenation cycling as well as density functional theory (DFT) calculations. The present work provides new insights in developing advanced nano-additives with unique structural and multifunctional designs towards LiBH 4 hydrogen storage. [ABSTRACT FROM AUTHOR]