First-principles study of LiFePO₄ modified by graphene and defective graphene oxide

The energy stability and electronic structural of graphene and defective graphene oxide (GO) parallel to the surface of LiFePO₄ (010) were theoretically investigated by using first-principles density functional theory calculations within the DFT + U framework. The calculated formation energy shows that GO coating on the surface of LiFePO₄ (010) is energetically favorable and has higher bond strength compared to graphene. The calculation of the electronic structure indicates that the emergence of band in-gap states originates from graphene coating, with adsorbed O atoms contributing significantly above the Fermi level. Electron density difference indicate that GO stands on the LFP (010) surface through C-O and Fe-O bonds, rather than relying on van der Waals forces placed parallel to the LFP crystal, with the chemical bond at the LFP/GO interface (Fe-O-C) both anchoring the coated carbon layer and promoting electron conductivity at the interface. In addition, LFP/GO shows superior electrochemical performance, Atomic Populations suggests that the average Fe-O bonding on the surface of LiFePO₄ (010) was clearly changed after graphene or GO coating, which led to the expansion of Li⁺ channels and favored the migration insertion and extraction of Li⁺.