Theoretical study of the hydrogen release mechanism from a lithium derivative of ammonia borane, LiNH2BH3-NH3BH3

► Combination of LiNH2BH3 and NH3BH3 leads to an even better compound for H2 release. ► The energy barrier for H2 release from LiNH2BH3-NH3BH3 is strongly reduced. ► Initial formation of a six-membered ring is responsible for the barrier reduction.