  Inspired by a recent experimental and theoretical study [Yang et al., 2017],
wherein protrusions in graphene have been proposed as an effective strategy to
enhance the performance of sodium ion batteries, a comprehensive study of the
effects of phosphorus doping in graphene on adsorption and diffusion behaviour
of Li is carried out by using density functional theory. We find that
protrusion introduced by P-dopant in graphene enhances the adsorption of a
single Li atom onto the anode due to an additional partial covalent bonding
character between Li and carbon atoms of the substrate. However, with increase
in concentration of Li atoms, they tend to form clusters which may lead to
dendrite growth and hence battery failure. Finite density of states at Fermi
level ensures the electronic conductivity of the P-doped graphene before and
after the adsorption of a Li atom. No momentous variation in DOS is observed
except a small up shift in Fermi level with increased Li concentration. The
presence of such protrusions acts as trapping centres for Li and hinders their
migration over the substrate, leading to poor cycling performance of anode.
This atomic level study will act as a useful guideline for further development
of anode materials for novel battery technologies.
