Abstract
In this generation, the importance of and the demands from the energy storage devices are much more than before because of the environmentally friendly issue arising with the technology developing. This investigation revealed the lithium sulfur battery which is one of the most promising energy storage materials in the next generation due to high energy density and economic price of the sulfur. Nevertheless, the sulfur which has poor electron conductivity was insulated, so the active sulfur was not fully utilized. The intermediate, long chain lithium sulfide can easily dissolve into electrolyte; as a result, the active material lost, resistance increased and capacity decayed. In order to solve these problems, we fabricated ZnS as the precursor, then we coated anatase TiO2 and carbon on the surface. Finally, S2- ions were oxidized by Fe3+ ions to form S/TiO2/C structure. The TiO2/C shell combined the advantages of physically separating particles, chemical trapping the lithium sulfide, while graphic carbon provided improved electronic conductivity. When the molar ratio of ZnS/TEOTi was 15, the sulfur weight percent of S/TiO2 was 77 %. The capacity of S/TiO2 was 733 mAhg-1 (0.5 C) at 100th cycle. The capacity of S/TiO2 was higher than the capacity of commercial nano sulfur which was 560 mAhg-1 (0.5 C) at 100th cycle. The optimized S/TiO2/C cathode material which had 56.8 wt% sulfur and 18.3 wt% graphic carbon was made from ZnS/TiO2/C and still maintained the capacity at 905 mAhg-1 (0.5 C) after 100 cycles and had the lowest resistance when the carbon source was 14 wt%.