On the surface chemical aspects of very high energy density, rechargeable Li-sulfur batteries

Li(metal)-sulfur (Li-S) systems are among the rechargeable batteries of the highest possible energy density due to the high capacity of both electrodes. The surface chemistry developed on Li electrodes in electrolyte solutions for Li-S batteries was rigorously studied using Fourier transform infrared and X-ray photoelectron spectroscopies. A special methodology was developed for handling the highly reactive Li samples. It was possible to analyze the contribution of solvents such as 1-3 dioxolane, the electrolyte LiN (S O₂ C F ₃)₂, polysulfide (Li₂ S_n), and LiN O₃ additives to protective surface films that are formed on the Li electrodes. The role of LiN O₃ as a critical component whose presence in solutions prevents a shuttle mechanism that limits the capacity of the sulfur electrodes is discussed and explained herein.