First-principles study of lithium intercalation and diffusion in oxygen-defective titanium dioxide

Titanium dioxide has attracted considerable attention as a potential alternative anode material in lithium-ion rechargeable batteries. In recent years, the incorporation of oxygen vacancy into such anode materials has been demonstrated to improve electrical conductivity, cycling stability, and rate performance through experimental studies. In this work, lithium intercalation and diffusion behavior in pristine and oxygen-defective TiO₂ were studied by first principles based on density functional theory calculations. Total energies of possible intercalation sites were first calculated to find the most favorable site in the three commonly used polymorphs: anatase, rutile, and TiO₂(B). Furthermore, the energy barriers of possible paths for lithium diffusion from one stable site to another have been calculated by the climbing image nudged elastic band method. The electronic structures are also presented to compare conductivities of pristine and oxygen-defective TiO₂. Our results indicate that although all three phases show enhanced conductivity via oxygen-defect introduction, TiO₂(B) is the best choice for lithium intercalation and diffusion as potential anode materials, having the lowest intercalation energy and lithium diffusion barrier, both of which are expected to result in better battery performance.