High Sulfur Content Material with Stable Cycling in Lithium-Sulfur Batteries

Preefer, M. B., Oschmann, B., Hawker, C. J., Seshadri, R., Wudl, F.
Angew. Chem. Int. Ed.
2017
Volume 56, Issue 47, Pages 15118–15122

We demonstrate a novel crosslinked disulfide system as a cathode material for Li-S cells that is designed with the two criteria of having only a single point of S−S scission and maximizing the ratio of S−S to the electrochemically inactive framework. The material therefore maximizes theoretical capacity while inhibiting the formation of polysulfide intermediates that lead to parasitic shuttle. The material we report contains a 1:1 ratio of S:C with a theoretical capacity of 609 mAh g−1. The cell gains capacity through 100 cycles and has 98 % capacity retention thereafter through 200 cycles, demonstrating stable, long-term cycling. Raman spectroscopy confirms the proposed mechanism of disulfide bonds breaking to form a S−Li thiolate species upon discharge and reforming upon charge. Coulombic efficiencies near 100 % for every cycle, suggesting the suppression of polysulfide shuttle through the molecular design.