Synthesis and electrochemical performance of TiO_2-sulfur composite cathode materials for lithium-sulfur batteries

摘要

Titania-sulfur (TiO_2-S) composite cathode materials were synthesized for lithium-sulfur batteries. The composites were characterized and examined by X-ray diffraction, nitrogen adsorption/desorption measurements, scanning electron microscopy, and electrochemical methods, such as cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. It is found that the mesoporous TiO_2 and sulfur particles are uniformly distributed in the composite after a melt-diffusion process. When evaluating the electrochemical properties of as-prepared TiO_2-S composite as cathode materials in lithium-sulfur batteries, it exhibits much improved cyclical stability and high rate performance. The results showed that an initial discharge specific capacity of 1,460 mAh/g at 0.2 C and capacity retention ratio of 46.6 % over 100 cycles of composite cathode, which are higher than that of pristine sulfur. The improvements of electrochemical performances were due to the good dispersion of sulfur in the pores of TiO_2 particles and the excellent adsorbing effect on polysulfides of TiO_2.