Elucidating the reaction kinetics of lithium–sulfur batteries by operando XRD based on an open-hollow S@MnO2 cathode

Abstract

Quantitatively elucidating the reaction kinetics of Li–sulfur (Li–S) batteries is always crucial in optimizing cathode structures but challenging as well. Herein, we study and compare the reaction mechanism and kinetics of Li–S batteries via operando X-ray diffraction (XRD) and quantitative analysis based on several cathode structures. Operando XRD indicates that β-S₈ has different nucleation orientations on MnO₂ and carbon surfaces due to the different surface free energies. The quantitative analysis reveals that polysulfides encapsulated in MnO₂ nanosheets result in fast Li₂S and β-S₈ nucleation in the discharge and charge processes, respectively. It also shows that open-hollow S@MnO₂ exhibits faster S consumption and higher sulfur utilization than the solid core–shell S@MnO₂ and carbon black/S. Our work provides deep insight into the reaction mechanism and kinetics of Li–S batteries and indicates that the cathode structures and host materials play critical roles in enhancing the reaction kinetics.