Improvement of Surface Structure and Enhancement of Conductivity of LiFePO4 Surface by Graphene and Graphene-Like B-C-N Coating

Density functional theory calculations are used to investigate the surface structure and electric conductivity of the (010) surface of LiFePO4 coated with graphene or graphene-like B-C-N. The calculations indicate that the interaction between the coating and LiFePO4 (010) surface improves the electric conductivity of the LiFePO4 (010) surface. The band gap decreases from 3.3 to 2.1 eV when the LiFePO4 (010) surface is coated with graphene. When the LiFePO4 (010) surface is coated with graphene-like B-C-N, the valence band maximum and conduction band minimum are still dominated by Fe-3d orbitals; however, two in-gap states with an interval of 0.6 eV appear in the band gap, which are attributed to the bonding interaction between graphene-like B-C-N and the LiFePO4 (010) surface.