Density-functional study of LixMoS2 intercalates (0<=x<=1)

TL;DR

This study uses density-functional theory to analyze the stability, structural phases, and electronic properties of lithium intercalated MoS2, revealing phase transition points and electronic behavior changes with varying lithium content.

Contribution

It provides new insights into the phase transition threshold and electronic properties of LixMoS2 for different allotropes and lithium concentrations.

Findings

Octahedral Li intercalation is most favorable in both allotropes.

Phase transition from 2H to 1T occurs around x ~ 0.4.

Monoclinic Li1.0MoS2 is a semiconductor with a 1.1 eV band gap.

Abstract

The stability of Lithium intercalated 2H- and 1T allotropes of Molybdenum disulfide (LixMoS2) is studied within a density-functional theory framework as function of the Li content (x) and the intercalation sites. Octahedral coordination of Li interstitials in the van der Waals gap is found as the most favorite for both allotropes. The critical content of Lithium, required for the initialization of a 2H->1T phase transition is estimated to x ~ 0.4. For smaller Li contents the hexagonal 2H crystal structure is not changed, while 1T-LixMoS2 compounds adopt a monoclinic lattice. All allotropic forms of LixMoS2 - excluding the monoclinic Li1.0MoS2 structure - show metallic-like character. The monoclinic Li1.0MoS2 is a semiconductor with a band gap of 1.1 eV. Finally, the influence of Li intercalation on the stability of multiwalled MoS2 nanotubes is discussed within a phenomenological model.