Understanding Li interaction in TiO2/graphene composites for high-performance Li-ion battery anodes: A first principles study

Composite materials consisting of TiO2 and graphene (TiO2/GR) have exciting properties that could make them suitable as anode material for Li-ion batteries. Systematic density functional theory (DFT) calculations were performed to investigate the TiO2/GR energy-storage mechanism, adsorption sites and diffusion pathways of Li ions in TiO2/GR. Its interface and the region outside graphene were studied for identifying stable surface sites. The adsorption energies are dominated by van der Waals interactions. Li diffusion along the graphene plane was the most favorable with a diffusion energy barrier of 0.24 eV, whereas the probability of diffusion at the interface is low, due to the barrier of 3 eV. The composite exhibited a higher specific charge-storage capacity than other van der Waals heterostructures. The TiO2/GR interface retains a large amount of charge implying that the TiO2/GR composite shows suitable electrochemical properties for use as anode in lithium-ion batteries.