Kinetically-Driven Phase Transformation during Lithiation in Copper Sulfide Nanoflakes

Kai He*, Zhenpeng Yao, Sooyeon Hwang, Na Li, Ke Sun, Hong Gan, Yaping Du, Hua Zhang, Chris Wolverton, Dong Su

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


Two-dimensional (2D) transition metal chalcogenides have been widely studied and utilized as electrode materials for lithium ion batteries due to their unique layered structures to accommodate reversible lithium insertion. Real-time observation and mechanistic understanding of the phase transformations during lithiation of these materials are critically important for improving battery performance by controlling structures and reaction pathways. Here, we use in situ transmission electron microscopy methods to study the structural, morphological, and chemical evolutions in individual copper sulfide (CuS) nanoflakes during lithiation. We report a highly kinetically driven phase transformation in which lithium ions rapidly intercalate into the 2D van der Waals-stacked interlayers in the initial stage, and further lithiation induces the Cu extrusion via a displacement reaction mechanism that is different from the typical conversion reactions. Density functional theory calculations have confirmed both the thermodynamically favored and the kinetically driven reaction pathways. Our findings elucidate the reaction pathways of the Li/CuS system under nonequilibrium conditions and provide valuable insight into the atomistic lithiation mechanisms of transition metal sulfides in general.

Original languageEnglish (US)
Pages (from-to)5726-5733
Number of pages8
JournalNano letters
Issue number9
StatePublished - Sep 13 2017


  • Copper sulfides
  • CuS
  • electrochemistry kinetics
  • in situ TEM
  • lithium ion battery

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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