Carbon Coating of LiFePO4 Can Be Strengthened by Sc and Ti

Carbon coating substantially promotes electron transport through LiFePO4 nanoparticles at the positive electrode in Li-ion batteries and approaches to forming thin, tightly attached, and uniform carbon layers are extremely desirable. On the basis of our recent first principles computational discovery that the graphite crystallites are more likely standing on the LiFePO4 (010) surface via C-O bonding rather than lying on van der Waals forces, we have in this work searched promising co-coating substances which can reinforce the perpendicular orientation of graphite crystallites by strengthening the C/LiFePO4 binding. Among the three supervalent elements we have studied, Sc (3+), Ti (4+), and V (5+), Sc and Ti are found to show good performance. The binding energy of perpendicular graphite on the LiFePO4 (010) surface increases noticeably from 0.52 to 0.58 (Sc) and 0.61 (Ti) eV/angstrom, whereas the binding of a parallel graphene sheet with the same surface is nearly unchanged. A strengthened perpendicular graphite orientation is very welcome for leaving diffusion channels of Li unblocked.