Effect of rich R-TiO ₂ on the rate and cycle properties of Li ₄ Ti ₅ O ₁₂ as anode for lithium ion batteries

Li ₄ Ti ₅ O ₁₂ (LTO) with rich R-TiO ₂ (17.06, 23.69, and 34.42 wt%), namely, R-TiO ₂ @Li ₄ Ti ₅ O ₁₂ composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO ₂ change with the titanium dioxide content. EIS measurements showed that with increasing R-TiO ₂ content, both its charge transfer impedance (R _ct ) and lithium ion diffusion coefficient (D _Li ) decreased. The changes of R _ct and D _Li caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li ₄ Ti ₅ O ₁₂ . The rate performance is positively related to D _Li , while the cycle property is negatively correlated with R _ct , indicating that the rate performance is mainly related to D _Li , while R _ct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.