Revisiting Intercalation‐Induced Phase Transitions in 2D Group VI Transition Metal Dichalcogenides

Abstract

Intercalation of alkali metals is widely studied to introduce a structural phase transition from 2H to 1T′ in 2D group VI transition metal dichalcogenides (TMDCs). This highly efficient phase transition method has enabled an access to a library of phases with novel physical and chemical properties attractive for functional devices and electrochemical catalysis. However, despite numerous studies that have predicted that charge doping mainly contributes to the structural phase transition in the intercalation process, a mechanistic understanding of the phase transition at the atomic level has not been fully revealed. Furthermore, the coupled effects of strain and other intrinsic or extrinsic factors on the intercalation‐induced phase transition have not been quantitatively determined. Herein, the progress of the intercalation‐induced phase transition is briefly overviewed and the knowledge gaps in the current understanding of phase transition and intercalation in 2D TMDCs are highlighted. To fully gain the microscopic picture of the intercalation‐induced phase transition, in situ multimodal probes to monitor the real‐time structure−property relationship during intercalation are suggested. The proposed research directions further direct material scientists to efficiently engineer phase transition pathways in 2D materials to explore novel functional phases.

A Gapped Phase in Semimetallic Td‐WTe2 Induced by Lithium Intercalation

“…Adapted under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0). [ 20 ] Copyright 2021, The Authors, published by Wiley‐VCH. b) Side‐view of lithium intercalation in the van der Waals gaps of T d ‐WTe 2 (W: gray, Te: gold, Li: green).…”

A systematic computational investigation of lithiation-induced structural phase transitions of O-functionalized MXenes

“…Lithiation-induced phase transition occurs not only in the above traditional bulk materials, but also in 2D materials. [12][13][14][15] Among 2D materials, the phase transition of TMDs during lithiation has captured extensive research interest. In TMDs with the formula MX 2 (M = Mo, W; X = S, Se, Te), phase transitions of MoS 2 , MoSe 2 , WS 2 and WSe 2 from the semiconducting trigonal prismatic 2H phase to the metallic octahedral 1T phase or the distorted 1T 0 phase induced by the intercalations of Li or Na ions have been predicted by theoretical calculations [16][17][18][19][20] and further are observed using experimental techniques.…”

Antioxidant Triggered Metallic 1T’ Phase Transformations of Chemically Exfoliated Tungsten Disulfide (WS2) Nanosheets

“…However, because of the especially small atomic size of Li, together with the fact that initial TMDC bulk powder is not perfectly exfoliated into monolayers, there remain a few multilayered sheets, certain Li residues are difficult to completely remove, thereby presumably still existing inside the multilayered TMDC sheets. It is well-known that Li atoms can induce phase transformations from 2H to 1T', [17,18] hence, it stands to reason that these Li or LiO x residues can be leveraged toward chemically accelerating the metallic phase transformations. While previous studies of 2D TMDCs-based materials recognized the possibility of its chemical versatility to modulate their electrical modulation and the effect on the surface activity, [19] to the best of our knowledge, chemically triggered phase transformation on the 2D materials has not been report yet.…”