New insight into the atomic structure of electrochemically delithiated O3-Li(1- x)CoO2 (0 ≤ x ≤ 0.5) nanoparticles

Xia Lu, Yang Sun, Zelang Jian, Xiaoqing He, Lin Gu, Yong Sheng Hu, Hong Li, Zhaoxiang Wang, Wen Chen, Xiaofeng Duan, Liquan Chen, Joachim Maier, Susumu Tsukimoto, Yuichi Ikuhara

Research output: Contribution to journalArticlepeer-review

111 Citations (Scopus)


Direct observation of delithiated structures of LiCoO2 at atomic scale has been achieved using spherical aberration-corrected scanning transmission electron microscopy (STEM) with high-angle annular-dark-field (HAADF) and annular-bright-field (ABF) techniques. The ordered Li, Co, and O columns for LiCoO2 nanoparticles are clearly identified in ABF micrographs. Upon the Li ions extraction from LiCoO2, the Co-contained (003) planes distort from the bulk to the surface region and the c-axis is expanded significantly. Ordering of lithium ions and lithium vacancies has been observed directly and explained by first-principles simulation. On the basis of HAADF micrographs, it is found that the phase irreversibly changes from O3-type in pristine LiCoO2 to O1-type LixCoO 2 (x ≈ 0.50) after the first electrochemical Li extraction and back to O2-type LixCoO2 (x ≈ 0.93) rather than to O3-stacking after the first electrochemical lithiation. This is the first report of finding O2-LixCoO2 in the phase diagram of O3-LiCoO2, through which the two previously separated LiCoO 2 phases, i.e. O2 and O3 systems, are connected. These new investigations shed new insight into the lithium storage mechanism in this important cathode material for Li-ion batteries.

Original languageEnglish
Pages (from-to)6192-6197
Number of pages6
JournalNano Letters
Issue number12
Publication statusPublished - 2012 Dec 12
Externally publishedYes


  • Li-ion batteries
  • LiCoO
  • scanning transmission electron microscopy (STEM)
  • structural evolution

ASJC Scopus subject areas

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


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