Correlation between long range and local structural changes in Ni-rich layered materials during charge and discharge process

Shiyao Zheng, Chaoyu Hong, Xiaoyun Guan, Yuxuan Xiang, Xiangsi Liu, Gui-Liang Xu, Rui Liu, Guiming Zhong, Feng Zheng, Yixiao Li, Xiaoyi Zhang, Yang Ren, Zonghai Chen, Khalil Amine, Yong Yang*

*Corresponding author for this work

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

145 Citations (Scopus)

Abstract

Ni-rich cathode materials can deliver higher energy density with a lower cost compared with other conventional layered oxide materials. However, the cycling performance of Ni-rich materials needs further improvement, and the irreversible phase transformation related to the cell failure is not fully understood yet. Although an H1–H2–H3 structural change process is revealed, a more specific explanation about the difference of these hexagonal phases is needed for deeper comprehension and further targeted modification of Ni-rich materials. In this work, the different phase transformation mechanisms of LiNi0.6Co0.2Mn0.2O2 (NCM622) and LiNi0.8Co0.1Mn0.1O2 (NCM811) are investigated by C X-ray diffraction (XRD) measurement, and the relationship between structural change and capacity degradation is discussed, showing that H3 phase can be harmful for cycling. In addition, 6Li solid state nuclear magnetic resonance (ss-NMR) experiments are carried out for detecting the Li chemical environment at different state of charge, and the data can be associated with structural change obtained from in operando XRD results. From the analysis mentioned above, a new explanation of H1/H2/H3 is given, and a relationship between long range and local structural change has been put forward for the first time.
Original languageEnglish
Pages (from-to)336-343
JournalJournal of Power Sources
Volume412
DOIs
Publication statusPublished - 1 Feb 2019
Externally publishedYes

Bibliographical note

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Research Keywords

  • In operando XRD
  • Li local environment
  • Ni-rich materials
  • Solid-state NMR
  • Structural change

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