Enhancing capacity and transport kinetics of C@TiO2 core–shell composite anode by phase interface engineering

Abstract

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 core–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 g−1 at a current density of 37 mA g−1 after 100 cycles) and Li-ion diffusion coefficient (4.0 × 10–14 cm2 s−1) than the amorphous C (178 mAh g−1 and 2.9 × 10–15 cm2 s−1) and anatase TiO2 (120 mAh g−1 and 1.6 × 10–15 cm2 s−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 g−1 at 37 mA g−1 after 100 cycles) and Li-ion diffusion coefficient (3.2 × 10–13 cm2 s−1), and excellent rate capability (368.6 mAh g−1 at 444 mA g−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.