Surface Properties of Lithium Sulfide from First Principles

Research interest in Lithium/Sulfur batteries has risen dramatically most recently due to the system’s potential to replace lithium-ion technology in selected applications. The Li/S system seems promising due to its high theoretical specific capacity (1166 mAh/g) and cheap, readily-available constituent materials. Implementation, however, has been plagued by problems in achieving suitable reversibility. These problems are due primarily to a lack of bulk electrical conductivity in the battery couple’s discharge product, Li₂S, which disallows a reverse electrochemical reaction. It is possible, however, that this material has one or more stable surfaces which do conduct. In this work, we use ab-initio methods to study the thermodynamic stability of varying surfaces of Li₂S, and whether these surfaces manifest conducting properties. We also study the adsorption trends of Li and S onto the most stable surface in order to better understand the growth mechanism of Li₂S films.