Heterointerface effects on lithium-induced phase transitions in intercalated MoS2

TL;DR

This study investigates how heterointerfaces in 2D materials, specifically MoS2 with hBN, influence lithium-induced phase transitions, revealing that thermodynamic stabilization can be counteracted by kinetic barriers, affecting electrochemical behavior.

Contribution

The paper combines ab initio calculations and in situ spectroscopy to show that heterointerfaces can both stabilize and hinder phase transitions in 2D materials, highlighting complex interfacial effects.

Findings

Li intercalation stabilizes 1T phase at the MoS2-hBN interface by ~100 mJ/m².

Phase transition voltage remains unchanged in heterostructures during intercalation.

Heating lowers the transition voltage, indicating kinetic barriers influence phase change.

Abstract

The intercalation-induced phase transition of MoS2 from the semiconducting 2H to the semimetallic 1T' phase has been studied in detail for nearly a decade; however, the effects of a heterointerface between MoS2 and other two-dimensional (2D) crystals on the phase transition have largely been overlooked. Here, ab initio calculations show that intercalating Li at a MoS2-hexagonal boron nitride (hBN) interface stabilizes the 1T phase over the 2H phase of MoS2 by ~ 100 mJ m-2, suggesting that encapsulating MoS2 with hBN may lower the electrochemical energy needed for the intercalation-induced phase transition. However, in situ Raman spectroscopy of hBN-MoS2-hBN heterostructures during electrochemical intercalation of Li+ shows that the phase transition occurs at the same applied voltage for the heterostructure as for bare MoS2. We hypothesize that the predicted thermodynamic stabilization of the 1T'-MoS2-hBN interface is counteracted by an energy barrier to the phase transition imposed by the steric hindrance of the heterointerface. The phase transition occurs at lower applied voltages upon heating the heterostructure, which supports our hypothesis. Our study highlights that interfacial effects of 2D heterostructures can go beyond modulating electrical properties and can modify electrochemical and phase transition behaviors.