We describe the preparation of hard carbon samples from epoxy resins.
These materials are shown by wide angle X-ray diffraction to be constr
ucted of graphene sheets of small lateral extent (about 25 Angstrom in
diameter). By controlling the synthesis conditions, it is possible to
prepare materials wherein the fraction of graphene sheets present as
single layers can be adjusted. Using small angle X-ray scattering, we
show that these materials incorporate small nanopores between the sing
le layers, which are about 15 Angstrom in diameter. This suggests that
the single layers are arranged more or less like a ''house of cards''
. Lithium can be inserted reversibly into these materials and the amou
nt of lithium that can be inserted increases as the fraction of single
layers in the sample increases. This suggests that the mechanism of l
ithium insertion in these materials is surface adsorption of lithium o
n the internal surfaces of the singlelayer graphene sheets. We compare
the insertion of lithium in these carbons to that which occurs in sof
t carbons with insignificant numbers of single layers and no measurabl
e nanoporosity.