Superior lithium-ion storage performances of carbonaceous microspheres with high electrical conductivity and uniform distribution of Fe and TiO ultrafine nanocrystals for Li-S batteries

Carbonaceous microspheres with well-developed micro- and mesopores, a high electrical conductivity, uniform distribution of Fe and TiO ultrafine nanocrystals have been developed as a sulfur host material for lithium-sulfur batteries. TiO nanocrystals were applied to these microspheres as a bifunctional material to achieve a high electrical conductivity and efficient lithium polysulfide trapping. Metallic Fe nanocrystals were used as an efficient nanocatalyst to transform the amorphous carbon in the microspheres into highly conductive graphitic carbon. These microspheres have demonstrated excellent material properties for hosting sulfur. The discharge capacities of the modified carbonaceous microspheres and original amorphous carbonaceous microspheres loaded with 70 wt% sulfur for the 450th cycle at a current rate of 0.8 C were 685 and 195 mA h g−1, respectively, and their capacity retentions measured from the 10th cycle were 79.6 and 32.8%, respectively. The TiO nanocrystals trap polysulfides formed during the discharge process, which improves the cycling performance of the modified carbonaceous electrodes. The synergetic effects of the high electrical conductivity and graphitic carbon formation result in superior discharge capacity and high rate performance for these electrodes.