Heterogeneity in Li-S Batteries Resolved through Operando Synchrotron Diffraction Studies

Abstract

Lithium-Sulfur (Li-S) batteries are promising candidates for electric vehicle applications due to their very high theoretical specific capacity (1670 mAh/g) and the tremendous availability and low cost of elemental sulfur. However, their practical capacity is substantially smaller (~1000 mAh/g) and their cycling performance is hindered by numerous technical challenges caused by issues on both cathode and anode sides of the system. While Li-S cells with extended cycling lifetimes can be built, they are typically only effective when using excess electrolytes and applied pressure, limiting their utility for practical applications. To gain deeper insights into the origin of missing capacity and the capacity fade of Li-S cells, we conducted operando studies on Li-S pouch cell batteries using synchrotron powder diffraction techniques. This approach enabled us to sensitively track the various crystalline phases involved in the cycling of Li-S batteries and to resolve a variety of inhomogeneities within cells that may affect their performance and lifetime.