On the Surface Chemical Aspects of Very High Energy Density, Rechargeable Li–Sulfur Batteries

TLDR

Li–S batteries achieve the highest energy density among rechargeable systems because both lithium metal and sulfur electrodes provide large capacities. The authors investigated Li electrode surface chemistry in Li–S electrolytes using FTIR and XPS, employing a novel handling protocol for highly reactive lithium samples. They found that solvents such as 1,3‑dioxolane, the electrolyte, polysulfides, and additives form protective surface films on Li, and that a specific additive prevents the polysulfide shuttle, preserving sulfur electrode capacity.

Abstract

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 , polysulfide , and additives to protective surface films that are formed on the Li electrodes. The role of 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.