Contribution of Metal Additives on the Electrochemical Process Involving Solid Sulfur and Soluble Lithium Polysulfide in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have attracted remarkable attention as next-generation batteries due to their low cost and high theoretical specific energy density. However, they have encountered several difficulties, including low specific capacity due to the insulating nature of sulfur as well as poor cycle performance. Here, we introduce the Li-S batteries using metal-deposited graphite as a positive electrode, together with S-8 and Li2S8 as active materials to achieve high initial discharge capacity and improved cyclability. Galvanostatic charge-discharge measurements for the S-8-impregnated electrode highlight the positive effect of Au additives on the initial discharge capacity (mAh cm(-3)); 48.1 (G)<56.1 (Ag/G)<84.1 (Au/G). Furthermore, improved cyclability was observed for the Au-decorated electrode with a Li2S8 catholyte system; capacity retention rate was in order of Ag/G<G<Au/G. The validity of the design strategy for both electrode and active material was confirmed by observing the highest discharge capacity at the 50th cycle for Au-decorated electrode (84.8 mAh cm(-3)) using both S-8 and Li2S8 active materials. We concluded that (1) the enhanced electrochemical solid reversible arrow liquid conversion of sulfur and (2) high sulfur affinity of Au particle enabled the efficient utilization of insulated solid sulfur active materials (S-8 and Li2S) as well as liquid lithium polysulfide intermediates, contributing to the high initial discharge capacity and better cyclability.