Intercalation processes and diffusion paths of lithium ions in spinel-type structuredLi1+xTi2O4: Density functional theory study

Abstract

Intercalation processes and corresponding diffusion paths of Li ions into spinel-type structured ${\mathrm{Li}}_{1+x}{\mathrm{Ti}}_2{\mathrm{O}}_4$ $(0⩽x⩽0.375)$ are systematically studied by means of periodic density functional theory calculations for different compositions and arrangements. An analysis of the site preference for intercalation processes is carried out, while energy barriers for the diffusion paths have been computed in detail. Our results indicate that the Li insertion is thermodynamically favorable at octahedral sites $16c$ in the studied composition range, and Li migration from tetrahedral sites $8a$ to octahedral sites $16c$ stabilizes the structure and becomes favorable for compositions $x⩾0.25$. Diffusion paths from less stable arrangements involving Li migrations between tetrahedral and octahedral sites exhibit the lowest energy barrier since the corresponding trajectories and energy profiles take place across a triangle made by three neighboring oxygen anions without structural modification. Theoretical and experimental diffusion coefficients are in reasonable agreement.