Understanding the Reaction Mechanism of Lithium–Sulfur Batteries by In Situ/Operando X-ray Absorption Spectroscopy

Because of the high theoretical energy density of $$2600\, \hbox {Wh kg}^{-1}$$ , lithium–sulfur (Li–S) batteries are regarded as one of the most promising energy storage technologies to meet the increasing requirement from personal devices to automobiles. However, the practical application of Li–S batteries is still challenging due to technical obstacles, such as low sulfur utilization and poor lifetime. Therefore, understanding the electrode reaction mechanism is of critical importance to further improve the battery performance and lifetime. Here, we review recent progress in the application of in situ and operando X-ray absorption spectroscopy in characterizing Li–S batteries. We discuss in detail how this advanced technique helps researchers understand the redox process of the electrode materials as well as the influence of polymer binder and electrolyte additive on the polysulfide shuttle effect, which provide valuable information for designing better Li–S batteries. A general conclusion and critical further research directions are also provided at the end.