In nanocomposite electrodes, besides the synergistic effect that takes advantage of the merits of each component, phase interfaces between the components would contribute significantly to the overall electrochemical properties. However, the knowledge of such effects is far from being well developed up to now. The present work aims at a mechanistic understanding of the phase interface effect in C@TiO2 coreâ€"shell nanocomposite anode which is both scientifically and industrially important. Firstly, amorphous C, anatase TiO2 and C@anatse-TiO2 electrodes are compared. The C@anatase-TiO2 shows an obvious higher specific capacity (316.5 mAh gâ'1 at a current density of 37 mA gâ'1 after 100 cycles) and Li-ion diffusion coefficient (4.0 × 10â€"14 cm2 sâ'1) than the amorphous C (178 mAh gâ'1 and 2.9 × 10â€"15 cm2 sâ'1) and anatase TiO2 (120 mAh gâ'1 and 1.6 × 10â€"15 cm2 sâ'1) owing to the C/TiO2 phase interface effect. Then, C@anatase/rutile-TiO2 is obtained by a heat treatment of the C@anatase-TiO2. Due to an anatase-to-rutile phase transformation and diffusion of C along the anatase/rutile phase interface, additional abundant C/TiO2 phase interfaces are created. This endows the C@anatase/rutile-TiO2 with further boosted specific capacity (409.4 mAh gâ'1 at 37 mA gâ'1 after 100 cycles) and Li-ion diffusion coefficient (3.2 × 10â€"13 cm2 sâ'1), and excellent rate capability (368.6 mAh gâ'1 at 444 mA gâ'1). These greatly enhanced electrochemical properties explicitly reveal phase interface engineering as a feasible way to boost the electrochemical performance of nanocomposite anodes for Li-ion batteries. [ABSTRACT FROM AUTHOR]