The Reaction Mechanism of a Complex Intercalation System: In Situ X-ray Diffraction Studies of the Chemical and Electrochemical Lithium Intercalation in Cr4TiSe8

The intercalation reaction between Cr4TiSe8 and Li was investigated from a kinetic and an electrochemical perspective. The structural phase transition from monoclinic to trigonal symmetry was probed by in situ energy-dispersive X-ray diffraction (in situ EDXRD) for chemical intercalation with butyllithium (BuLi). A change in the kinetic mechanism was detected for the reaction at room temperature; this was interpreted in terms of a trend from phase boundary control to diffusion control. A single diffusion-controlled mechanism is obeyed at 60 °C. The electrochemical measurements and the corresponding in situ X-ray diffraction (in situ XRD) data revealed that the monoclinic host is intercalated up to the composition Lix≈0.1Cr4TiSe8 before the characteristic phase transition starts. The monoclinic phase undergoes complex structural changes in the following two-phase regime. Owing to the co-existence of two phases, the cell potential is constant for 0.1