Synthesis, characterization, and electrochemical performance of spherical nanostructure of Magnéli phase Ti₄O₇

In this paper, the electrically conductive of Magnéli phase Ti₄O₇ was successfully synthesized using TiO(NO₃)₂ as the precursor of titania in a reductive atmosphere at 1000 °C for 6 h, and characterized by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The SEM images clearly show the spherical shape and their average particle size is around 250 nm. The as-prepared Ti₄O₇ was used as an additive to prepare sulfur/Ti₄O₇ composite cathode. The cyclic voltammetry tests demonstrated the Ti₄O₇ can not only contribute to reduce the dissolution of polysulfides into electrolytes, but also improve the electrochemical reaction kinetics during charge–discharge processes. The effect of the Ti₄O₇ nanospheres heat treatment temperature on the sulfur/Ti₄O₇ cycling performance was also investigated. As a result, the cathode with nanospheres of Ti₄O₇ calcined at 1000 °C exhibited 930 mAh g⁻¹ of initial capacity and keeping the remaining capacity of 460 mAh g⁻¹ over 100 cycles, which could be improved due to its high specific surface area and nanosized structure.