Critical electronic structures controlling phase transitions induced by lithium ion intercalation in molybdenum disulphide

We report on first-principles studies of lithium-intercalation-induced structural phase transitions in molybdenum disulphide (MoS₂), a promising material for energy storage in lithium ion batteries. It is demonstrated that the inversion-symmetry-related Mo-S p-d covalence interaction and the anisotropy of d-band hybridization are the critical factors influencing the structural phase transitions upon Li ion intercalation. Li ion intercalation in 2H-MoS₂ leads to two competing effects, i.e. the 2H-to-1T transition due to the weakening of Mo-S p-d interaction and the D _6h crystal field, and the charge-density-wave transition due to the Peierls instability in Li-intercalated 2H phase. The stabilization of charge density wave in Li-intercalated MoS₂ originates from the enhanced electron correlation due to nearest-neighbor Mo-Mo d-d covalence interaction, conforming to the extended Hubbard model. The magnitude of charge density wave is affected by Mo-S p-d covalence interaction and the anisotropy of d-band hybridization. In 1T phase of Li-intercalated MoS₂, the strong anisotropy of d-band hybridization contributes to the strong Fermi surface nesting while the d-band nonbonding with S-p facilities effective electron injection.