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

Abstract

The intercalation reaction between Cr(4)TiSe(8) 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 degrees 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 Li(x approximately 0.1)Cr(4)TiSe(8) 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<x<0.7 and 0.9<x<3.0. The subsequent intercalation into the trigonal phase leads to a pronounced increase in the cell volume of the trigonal phase that stops at x approximately 0.8. At this point, the complete reduction of Ti(IV) gives rise to a voltage drop of the cell potential. XANES measurements revealed that the reduction of Ti(IV) occurs prior to the reduction of Cr(III).

In situ EDXRD study of the chemistry of aging of co-precipitated mixed Cu,Zn hydroxycarbonates – consequences for the preparation of Cu/ZnO catalysts

“…under hydrothermal conditions 26 or in intercalation/de-intercalation reactions. 27 In this work, we have combined in situ EDXRD with in situ UV-vis spectroscopy to study the mechanism of Cu/ZnO catalyst precursor aging.…”

Chemical and electrochemical insertion of Li into the spinel structure of CuCr2Se4: ex situ and in situ observations by X-ray diffraction and scanning electron microscopy

“…1 In the case of conducting/semiconducting hosts, the reversible uptake and release of guests may be accompanied by a change in the charge density of the host materials: electrons are transferred from the guest to the host lattice during intercalation which are then removed during deintercalation reaction and both reactions lead to significant changes in the physical properties of the host-guest compounds. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Besides the large synthetic potential of intercalation chemistry, the reversible insertion of Li into different host materials is the basis for the operation of rechargeable Li-ion batteries. [19][20][21][22] Many different materials have been tested and a variety of mechanisms can occur when Li reacts with the host material.…”

Intercalation as a versatile tool for fabrication, property tuning, and phase transitions in 2D materials

“…Trigonal Li x CrTi 0.25 Se 2 has a structure like intercalated layered TMDs. This phase transition from monoclinic to trigonal has been investigated by Behrens et al 226 A recent theoretical study by Musa et al 227 has shown that Liintercalation can lead to a structural phase transition from black to blue phosphorene in a two-step (lithiation and delithiation) process. In lithiation part, Li atom intercalated in black phosphorene act as a "catalyst" in the 'reactive region' of the lone pair of P atoms and breaks the P-P bonds in the arm-chair direction.…”

“…Trigonal Li x CrTi 0.25 Se 2 has a structure like intercalated layered TMDs. This phase transition from monoclinic to trigonal has been investigated by Behrens et al 226 , using energy-dispersive (ED) XRD. According to their report, intercalation of Cr 4 TiSe 8 takes place in several steps; monoclinic Li 0.1 Cr 4 TiSe 8 is formed at the first step, further Li concentration facilitates a phase transition and domains of trigonal Li x CrTi 0.25 Se 2 nucleate and grow.…”