Atomic-scale observation of electrochemically reversible phase transformations in SnSe 2 single crystals

Sungkyu Kim, Zhenpeng Yao, Jin Myoung Lim, Mark C. Hersam, Chris Wolverton, Vinayak P. Dravid, Kai He

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

2D materials have shown great promise to advance next-generation lithium-ion battery technology. Specifically, tin-based chalcogenides have attracted widespread attention because lithium insertion can introduce phase transformations via three types of reactions—intercalation, conversion, and alloying—but the corresponding structural changes throughout these processes, and whether they are reversible, are not fully understood. Here, the first real-time and atomic-scale observation of reversible phase transformations is reported during the lithiation and delithiation of SnSe 2 single crystals, using in situ high-resolution transmission electron microscopy complemented by first-principles calculations. Lithiation proceeds sequentially through intercalation, conversion, and alloying reactions (SnSe 2 → Li x SnSe 2 → Li 2 Se + Sn → Li 2 Se + Li 17 Sn 4 ) in a manner that maintains structural and crystallographic integrity, whereas delithiation forms numerous well-aligned SnSe 2 nanodomains via a homogeneous deconversion process, but gradually loses the coherent orientation in subsequent cycling. Furthermore, alloying and dealloying reactions cause dramatic structural reorganization and thereby consequently reduce structural stability and electrochemical cyclability, which implies that deep discharge for Sn chalcogenide electrodes should be avoided. Overall, the findings elucidate atomistic lithiation and delithiation mechanisms in SnSe 2 with potential implications for the broader class of 2D metal chalcogenides.

Original languageEnglish
Article number1804925
JournalAdvanced Materials
Volume30
Issue number51
DOIs
Publication statusPublished - Jan 1 2018

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Keywords

  • DFT calculations
  • In situ TEM
  • Lithium-ion batteries
  • Reversible phase transformations
  • Tin selenides

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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