Operando XRD for tracking the phase transition of the co-intercalation in layered cathode materials for Na-ion batteries

Solvent co-intercalation reactions have attracted considerable research interest due to their fast reaction kinetics, especially with respect to graphite anodes in sodium-ion batteries. However, electrochemical co-intercalation reactions in cathode materials have rarely been studied. Herein, we propose to use synchrotron radiation operando XRD to continuously track the phase transition of the co-intercalation process in a series of layered compounds (O3-NaxTiS2, NaCr0.33Ti0.67S2, NaCr0.5Ti0.5S2, and NaTi0.5V0.5S2) in different electrolyte systems (such as glyme-based, EC/DMC-based, PC-based, and THF-based). According to the obtained results, how the co-intercalation process carries out in a series of layered compounds, including in what kind of solvent, and under what kind of conditions, and how the reversibility of the co-intercalation is, will be understood, and provide guidance information in the further investigation of the co-intercalation process in layered cathode materials.