Fabrication of Magneli phase Ti4O7 nanorods as a functional sulfur material host for lithium-sulfur battery cathode

In this paper, we report a facile approach to synthesize pure Magneli phase Ti4O7 nanostructures via solvothermal processing and subsequent thermal treatment. The one-dimensional nanostructure of Ti4O7 nanorods (1D Ti4O7 NRs) was characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and high-resolution transmission electron microscopy (HRTEM). The as-obtained Ti4O7 NRs, with an average diameter of 150 nm, were used as sulfur host to prepare Ti4O7 NRs/sulfur cathode for lithium-sulfur (Li-S) batteries. Electrochemical measurements showed that the as-synthesized Ti4O7 NRs can improve the electrochemical reaction kinetics during the charge-discharge processes. The initial discharge capacity of the Ti4O7 NRs/sulfur cathode was 930 mAh g(-1), and the remaining capacity was 490 mAh g(-1) after 500 cycles at 1C, much higher than that of acetylene black/sulfur cathode. Electrochemical impedance spectroscopy (EIS) demonstrated Ti4O7 NRs/sulfur decreases the charge transfer resistance. Moreover, Ti4O7 NRs/sulfur composite exhibits low electrode polarization accompanied by a high lithium ion diffusion coefficient.