  Fullerene-based materials including C60 and doped C60 have previously been
proposed as anodes for lithium ion batteries. It was also shown earlier that n-
and p-doping of small molecules can substantially increase voltages and
specific capacities. Here, we study ab initio the attachment of multiple
lithium atoms to C60, nitrogen-doped C60 (n-type), and boron doped C60
(p-type). We relate the observed attachment energies (which determine the
voltage) to changes in the electronic structure induced by Li attachment and by
doping. We compare results with a GGA functional and a hybrid functional and
show that while they agree semi-quantitatively with respect to the expected
voltages, there are qualitative differences in the electronic structure. We
show that, contrary to small molecules, single atom n- and p-doping will not
lead to practically useful modulation of the voltage-capacity curve beyond the
initial stages of lithiation.
