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