Researchers from The University of Queensland (Australia) have devised a composite cathode material for lithium-sulfur batteries: graphene-wrapped carbon nanospheres with sulfur uniformly distributed in between, in which the carbon nanospheres act as the sulfur carriers. The graphene contributes to direct coverage of sulfur to inhibit the mobility of polysulfides, whereas the carbon nanospheres undertake the role of carrying the sulfur into the carbon network.
The composite achieves a high loading of sulfur (64.2 wt %) and provides a maximum discharge capacity of 1,394 mAh g−1 at a current rate of 0.1 C with stability up to 100 cycles. The composite also delivered 746 g–1 at 1 C and 604 mAh g–1 at 2 C.
The researchers attributed the improved electrochemical properties of this composite material to the dual functions of the carbon components, which effectively restrain the sulfur inside the carbon nano-network.
A paper on their work is published in Chemistry, a European Journal.
Wang, B., Wen, Y., Ye, D., Yu, H., Sun, B., Wang, G., Hulicova-Jurcakova, D. and Wang, L. (2014) “Dual Protection of Sulfur by Carbon Nanospheres and Graphene Sheets for Lithium–Sulfur Batteries,” Chem. Eur. J. doi: 10.1002/chem.201400385