Wednesday, 3 October 2018: 08:00
Mars 1/2/3/4 (Sunrise Center)
Lithium-sulfur (Li-S) batteries have been the subject of intensive research during the past decade as a next-generation conversion battery chemistry, owing to their higher theoretical gravimetric energy density (1672 mAh·g-1), as compared to the traditional intercalation Li-ion batteries of current use in portable electronics and hybrid electric vehicles. Although much progress has been made in the attempt to overcome the inherent problems associated with the use of insulating active materials -both sulfur and the final Li2S discharge product- many questions remain regarding the use of nanostructured sulfur-carbon cathodes and the formation of Li2S during cycling. By using first-principles calculations, here we present the early stages of Li2S growth on a typical carbon substrate, such as graphene, in order to shed light on the morphology and electronic properties of this insulating material that can lead to voltage decay, capacity fade and ultimately the stalling of the Li-S battery. Our findings provide conceptual guidance in the experimental search for the mechanisms driving the voltage and capacity fading of Li-S batteries upon growth of such reaction products, in an attempt to solve the structural instability and, therefore, help in the design of new nanostructured sulfur-carbon cathodes for Li-S batteries.