Formation of Perpendicular Graphene Nanosheets on LiFePO4: A First-Principles Characterization

Coating carbon layers on LiFePO 4 nanoparticles used in Li-ion batteries greatly increase the electron transport in this cathode material. Using first-principles density functional theory calculations, we have theoretically investigated the interaction energies of graphene lying parallel and perpendicular to a LiFePO4 (010) surface and have found that the perpendicular orientation is energetically favorable. Our computations suggest that graphene nanosheets prefer standing vertically on LiFePO 4 (010) using C–O and C–Fe bonding rather than spreading on it, as has been widely assumed. The interfacial chemical bonding both fastens the coated carbon layer and facilitates electron conductivity across the interface. By contrast, encapsulating LiFePO 4 with parallel graphene sheets does not increase electron conductivity across the interface.