Transport and Electrochemical Properties of Li 4 Ti 5 O 12 -Li 2 TiO 3 and Li 4 Ti 5 O 12 -TiO 2 Composites.

The study demonstrates that the introduction of the electrochemically inactive dielectric additive Li 2 TiO 3 to LTO results in a strong decrease in the grain boundary resistance of LTO-Li 2 TiO 3 (LTC) composites at a low concentration of Li 2 TiO 3 . With the increase in the concentration of Li 2 TiO 3 in LTC composites, the grain boundary resistance goes through a minimum and increases again due to the growth of the insulation layer of small Li 2 TiO 3 particles around LTO grains. For LTO-TiO 2 (LTT) composites, a similar effect was observed, albeit not as strong. It was found that LTC composites at low concentration of Li 2 TiO 3 have unusually high charge-discharge capacity exceeding the theoretical value for pure LTO. This effect is likely to be caused by the occurrence of the electrochemical activity of Li 2 TiO 3 in the vicinity of the interfaces between LTO and Li 2 TiO 3 . The increase in the capacity may be qualitatively described in terms of the model of two-phase composite in which there is the interface layer with a high capacity. Contrasting with LTC composites, in LTT composites, no capacity enhancement was observed, which was likely due to a noticeable difference in crystal structures of LTO and TiO 2 preventing the formation of coherent interfaces.