  We study polylithiated molecules as building blocks for hydrogen storage
materials, using first-principles calculations. $\clifour$ and $\olitwo$ bind
12 and 10 hydrogen molecules, respectively, with an average binding energy of
0.10 and 0.13 eV, leading to gravimetric densities of 37.8 and 40.3 weight % H.
Bonding between Li and C or O is strongly polar and $\hyd$ molecules attach to
the partially charged Li atoms without dissociating, which is favorable for
(de)hydrogenation kinetics. CLi$_n$ and OLi$_m$ molecules can be chemically
bonded to graphene sheets to hinder the aggregation of such molecules. In
particular B or Be doped graphene strongly bind the molecules without seriously
affecting the hydrogen binding energy. It still leads to a hydrogen storage
capacity in the range 5-8.5 wt % H.
