Observation of an intermediate state during lithium intercalation of twisted bilayer MoS2

Yecun Wu; Jingyang Wang; Yanbin Li; Jiawei Zhou; Bai Yang Wang; Ankun Yang; Lin-Wang Wang; Harold Y Hwang; Yi Cui

doi:10.1038/s41467-022-30516-z

Observation of an intermediate state during lithium intercalation of twisted bilayer MoS₂

Nat Commun. 2022 May 30;13(1):3008. doi: 10.1038/s41467-022-30516-z.

Authors

Yecun Wu^#^{1

2}, Jingyang Wang^#^{3

4}, Yanbin Li³, Jiawei Zhou³, Bai Yang Wang^{1

5}, Ankun Yang³, Lin-Wang Wang⁴, Harold Y Hwang^{6

7}, Yi Cui^{8

9}

Affiliations

¹ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
² Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
³ Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
⁴ Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA, USA.
⁵ Department of Physics, Stanford University, Stanford, CA, USA.
⁶ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. hyhwang@stanford.edu.
⁷ Department of Applied Physics, Stanford University, Stanford, CA, USA. hyhwang@stanford.edu.
⁸ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. yicui@stanford.edu.
⁹ Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA. yicui@stanford.edu.

^# Contributed equally.

Abstract

Lithium intercalation of MoS₂ is generally believed to introduce a phase transition from H phase (semiconducting) to T phase (metallic). However, during the intercalation process, a spatially sharp boundary is usually formed between the fully intercalated T phase MoS₂ and non-intercalated H phase MoS₂. The intermediate state, i.e., lightly intercalated H phase MoS₂ without a phase transition, is difficult to investigate by optical-microscope-based spectroscopy due to the narrow size. Here, we report the stabilization of the intermediate state across the whole flake of twisted bilayer MoS₂. The twisted bilayer system allows the lithium to intercalate from the top surface and enables fast Li-ion diffusion by the reduced interlayer interaction. The E_2g Raman mode of the intermediate state shows a peak splitting behavior. Our simulation results indicate that the intermediate state is stabilized by lithium-induced symmetry breaking of the H phase MoS₂. Our results provide an insight into the non-uniform intercalation during battery charging and discharging, and also open a new opportunity to modulate the properties of twisted 2D systems with guest species doping in the Moiré structures.

Abstract

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