Lithium Attachment to C60 and Nitrogen- and Boron-Doped C60: A Mechanistic Study.

Fullerene-based materials including C and doped C have previously been proposed as anodes for lithium ion batteries. It was also shown earlier that - and -doping of small molecules can substantially increase voltages and specific capacities. Here, we study ab initio the attachment of multiple lithium atoms to C, nitrogen-doped C (-type), and boron doped C (-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 (generalized gradient approximation) 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 - and -doping will not lead to practically useful modulation of the voltage-capacity curve beyond the initial stages of lithiation.