Lithiation in 2H-MoTe2 Nanoflakes

In several two-dimensional (2D) transition metal dichalcogenides (TMDs), lithium intercalation has been observed to induce a phase transition from the 2H phase to the 1T′ phase in the TMDs, leading to improvements in various applications. For MoTe₂, calculations have also predicted the same phase transition under the influence of electron doping, strain, or lithium intercalation. In this work, however, we experimentally demonstrate that electrochemically controlled lithium intercalation does not lead to the predicted phase change in 2H-MoTe₂. Instead, the 2H-MoTe₂ directly decomposes to molybdenum (Mo), tellurium (Te), and lithium telluride (Li₂Te) upon lithiation despite the significant electron doping achieved by the lithium intercalation into 2H-MoTe₂ flakes, probed using in situ Raman spectroscopy and in situ conductivity measurements. Performing the lithium intercalation on 2H-MoTe₂ flakes at higher temperatures also did not result in the 1T′ phase, suggesting that additional thermal energy did not facilitate the phase transition. Thus, our experiments directly challenge the theoretical prediction and point to a potentially high nucleation barrier for the 1T′ phase in MoTe₂. Our findings emphasize the importance of studying the phase transition pathways for lithium intercalation-induced phase transitions in 2D TMDs.