Rotation angle dependent Li intercalation and the induced phase transition in bilayer MoTe2

Abstract

In this work, taking twisted bilayer MoTe2 (tb-MoTe2) as an example, density functional theory (DFT) calculations are done to investigate the interlayer rotation angle dependent lithium intercalation as well as the induced 2H → 1T phase transition in two-dimensional layered materials. Both static equipotential energy diagrams and dynamic ab initio molecular dynamics simulations (AIMD) are utilized to obtain the reliable lithium diffusion pathways and barriers. The results reveal that the interlayer rotation leads to increased interlayer separation in tb-MoTe2, and provides a stable environment for Li insertion. Moreover, the diffusion barrier is substantially reduced with increasing twist angle, promoting the fast Li diffusion. At room temperature, the mobility of Li in tb-MoTe2 with the twist angle of θ = 21.79˚ and θ = 60˚ is increased by a factor of 10 and 105, respectively. The energy barrier for the 2H → 1T phase transition is lowered from 1.23 eV in the non-twisted MoTe2 to 0.88 eV in the tb-MoTe2 with a twist angle θ = 21.79˚ for a given concentration of inserted Li. Above all, the enhanced diffusion and lower critical electron concentration facilitate the 2H-1T phase transition in tb-MoTe2. The results provide valuable insights into the non-uniform intercalation and present an opportunity to modulate the phase transition of twisted 2D systems.