Phase boundary structure of LixFePO4 cathode material revealed by atomic-resolution scanning transmission electron microscopy

Akiho Nakamura, Sho Furutsuki, Shin Ichi Nishimura, Tetsuya Tohei, Yukio Sato, Naoya Shibata, Atsuo Yamada, Yuichi Ikuhara

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

A variety of cathode materials in lithium ion batteries exhibit phase separations during electrochemical reactions, where two phases with different Li compositions are in equilibrium across the phase interface. Because of the lattice mismatch between these phases, large structural distortions are introduced around the interface region. To characterize their potential effect upon the Li migration behavior, the phase interface structure should be determined accurately. In this study, we perform sophisticated structural analyses for phase interfaces in the well-known cathode material LixFePO4, using atomic resolution scanning transmission electron microscopy. The lattice deformation behavior and Li composition gradient are separately measured across the interface and superimposed after spatial calibrations. The combined result reveals that their relationship significantly deviates from simple models, such as Vegard's law or other higher order interpolations. Notably, the interface region has small lattice sizes comparable to the FePO4 phase, while having intermediate Li compositions. The origin of observed structure is discussed considering the local phase stability by estimating the pair distance variations of dominant attractive/repulsive ionic couples. Because of the nonlinear variations of each structural parameter, well-optimized experiments with high spatial resolutions and sufficient accuracies are required to correctly understand the phase interface structures.

Original languageEnglish
Pages (from-to)6178-6184
Number of pages7
JournalChemistry of Materials
Volume26
Issue number21
DOIs
Publication statusPublished - Nov 11 2014
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Phase boundary structure of Li<sub>x</sub>FePO<sub>4</sub> cathode material revealed by atomic-resolution scanning transmission electron microscopy'. Together they form a unique fingerprint.

  • Cite this

    Nakamura, A., Furutsuki, S., Nishimura, S. I., Tohei, T., Sato, Y., Shibata, N., Yamada, A., & Ikuhara, Y. (2014). Phase boundary structure of LixFePO4 cathode material revealed by atomic-resolution scanning transmission electron microscopy. Chemistry of Materials, 26(21), 6178-6184. https://doi.org/10.1021/cm5024986