Intermediate phases in sodium intercalation into MoS2 nanosheets and their implications for sodium-ion batteries

Qianqian Li, Zhenpeng Yao, Jinsong Wu*, Sagar Mitra, Shiqiang Hao, Tuhin Subhra Sahu, Yuan Li, Chris Wolverton, Vinayak P. Dravid

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

76 Scopus citations

Abstract

Alkali metal ion intercalation into layered transition-metal dichalcogenide structures is a promising approach to make next generation rechargeable batteries for energy storage. It has been noted that the number of Na-ions which can be reversibly intercalated and extracted per MoS2 is limited, and the chemical and electrochemical processes/mechanisms remain largely unknown, especially for nano-sized materials. Here, sodiation of MoS2 nanosheets are studied by in-situ electron diffraction and the phase transformations in sodiation are identified with the aid of DFT calculations to reveal the reaction mechanism. Several thermodynamically stable/metastable structures are identified in the sodiation pathway of MoS2 nanosheets, previously unnoticed in bulk MoS2. The gradual reduction of Mo4+ upon Na-ion intercalation leads to a transition of the Mo-S polyhedron from a trigonal prism to an octahedron around 0.375 Na per MoS2 inserted (i.e. Na0.375MoS2). When the intercalated Na-content is larger than 1.75 per MoS2 structural unit (i.e. Na1.75MoS2), the MoS2 layered structure collapses and the intercalation reaction is replaced by an irreversible conversion reaction with the formation of Na2S and metal Mo nanoparticles. The calculated sodiation pathways reproduce the experimental sodiation voltages. The current observations provide useful insights in developing sodium-ion batteries with high cycling stability.

Original languageEnglish (US)
Pages (from-to)342-349
Number of pages8
JournalNano Energy
Volume38
DOIs
StatePublished - Aug 2017

Keywords

  • DFT calculation
  • In-situ electron diffraction
  • In-situ transmission electron microscopy
  • Intercalation reaction
  • MoS anode
  • Sodium-ion battery

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)
  • Electrical and Electronic Engineering

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