Heterointerface Control over Lithium-Induced Phase Transitions in MoS₂ Nanosheets: Implications for Nanoscaled Energy Materials

Abstract

Phase transitions of two-dimensional nanomaterials and their heterostructures enable many applications including electrochemical energy storage, catalysis, and memory; however, the nucleation pathways by which these transitions proceed remain underexplored, prohibiting engineering control for these applications. Here, we demonstrate that the lithium intercalation-induced 2H-1T′ phase transition in MoS2 nanosheets proceeds via nucleation of the 1T′ phase at an atomically thin heterointerface by monitoring the phase transition of MoS2/graphene and MoS2/hexagonal boron nitride (hBN) heterostructures with Raman spectroscopy in situ during intercalation. We observe that graphene–MoS2 heterointerfaces require an increase of 0.8 V in applied electrochemical potential to nucleate the 1T′ phase in MoS2 as compared to hBN–MoS2 heterointerfaces. The increased nucleation barrier at graphene–MoS2 heterointerfaces is due to the reduced charge transfer from lithium to MoS2 at the heterointerface as lithium also dopes graphene based on ab initio calculations. Furthermore, we show that the growth of the 1T′ domain propagates along the heterointerface rather than through the interior of MoS2. Our results provide the first experimental observations of the heterogeneous nucleation and growth of intercalation-induced phase transitions in two-dimensional nanomaterials and heterointerface effects on their phase transitions. These insights have implications for the design of energy technologies and devices that rely upon the phase stability of nanostructured materials.

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

“…The detailed fabrication steps are described in our previous research papers. [22,23] For the liquid cells, the liquid electrolyte of 1 m LiPF 6 (EC/DEC, v:v = 50:50, battery-grade, Sigma-Aldrich) was injected into the cell to submerge the lithium and the device. For polymer cells, 0.227 g 1 m LiPF 6 solution was premixed with 0.475 g poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 1.145 g bisphenol A ethoxylate dimethacrylate (BEMA) in a tarnished glass vial stirred overnight inside the glovebox.…”

Lithium storage performance enhanced by lithiation-induced structural phase transitions of fluorinated MXenes

“…[12][13][14][15] The phase transitions of TMDs during lithiation have received significant attention among various 2D materials. The predictions of phase transitions in TMDs, [16][17][18][19][20] including MoS 2 , MoSe 2 , WS 2 , and WSe 2 , induced by the intercalation of Li or Na ions have been confirmed by various experimental techniques. 13,[17][18][19][20][21][22][23][24][25] These phase transitions involve a change from the semiconducting trigonal prismatic 2H phase to metallic octahedral 1T phase or a distorted 1T 0 phase.…”

“…The predictions of phase transitions in TMDs, [16][17][18][19][20] including MoS 2 , MoSe 2 , WS 2 , and WSe 2 , induced by the intercalation of Li or Na ions have been confirmed by various experimental techniques. 13,[17][18][19][20][21][22][23][24][25] These phase transitions involve a change from the semiconducting trigonal prismatic 2H phase to metallic octahedral 1T phase or a distorted 1T 0 phase. Additionally, the 1T phase of MoS 2 and WS 2 achieved through Li intercalation exhibit improved activity for hydrogen evolution reaction.…”

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

“…[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. 13,[17][18][19][20][21][22][23][24][25] The 1T phases of MoS 2 and WS 2 obtained by Li intercalations show enhanced hydrogen evolution reaction activity.…”

“…Though advanced experimental techniques have been developed, first-principles calculations still have the advantages for exploring crystal structures and have also achieved some successful cases in investigating phase transitions of 2D electrode materials. [16][17][18][19][20]28,29,44 Through exploring the energy change of lithiated structures during Li-ion intercalation in this paper, structural phase transitions of ten M 2 X-type MXenes are investigated systematically by first-principles calculations. And then the lithium storage properties and mechanism are also studied.…”