What determines the critical size for phase separation in LiFePO4 in lithium ion batteries?

Tetsu Ichitsubo, Takayuki Doi, Kazuya Tokuda, Eiichiro Matsubara, Tetsuya Kida, Tomoya Kawaguchi, Shunsuke Yagi, Shigeto Okada, Jun-ichi Yamaki

Research output: Contribution to journalArticle

Abstract

LiFePO4 characteristically shows a plateau voltage due to a two-phase (LiFePO4/FePO4) separation during the charge/discharge process in Li ion batteries. In this study, we clearly show that monodispersed nano-sized (about 10 nm) LiFePO4 particles exhibit a complete single-phase reaction without showing any plateau voltage. Since the elastic strain due to lattice mismatch between LiFePO4 and FePO4 would be easily released near the surface, elastic effects are usually expected to weaken, but, in contrast to this expectation, phase separation does not occur experimentally in such small nanoparticles. Consideration on the basis of only static thermodynamics is insufficient to explain why such a single-phase reaction occurs in nano-sized particles. In contrast, the mechanism of the single-phase reaction can be naturally understood, when we consider a kinetics concept based on the preferred wavelength for stable growth of the spinodal wave under such an elastic constraint.
Original languageEnglish
Pages (from-to)14532-14537
Number of pages6
JournalJournal of Materials Chemistry A
Volume1
Issue number46
Publication statusPublished - Sep 19 2013

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    Ichitsubo, T., Doi, T., Tokuda, K., Matsubara, E., Kida, T., Kawaguchi, T., Yagi, S., Okada, S., & Yamaki, J. (2013). What determines the critical size for phase separation in LiFePO4 in lithium ion batteries? Journal of Materials Chemistry A, 1(46), 14532-14537. http://hdl.handle.net/2433/193039