Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping

William C. Chueh, Farid El Gabaly, Joshua D. Sugar, Norman C. Bartelt, Anthony H. McDaniel, Kyle R. Fenton, Kevin R. Zavadil, Tolek Tyliszczak, Wei Lai, Kevin F. McCarty

Research output: Contribution to journalArticle

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Abstract

The intercalation pathway of lithium iron phosphate (LFP) in the positive electrode of a lithium-ion battery was probed at the ∼40 nm length scale using oxidation-state-sensitive X-ray microscopy. Combined with morphological observations of the same exact locations using transmission electron microscopy, we quantified the local state-of-charge of approximately 450 individual LFP particles over nearly the entire thickness of the porous electrode. With the electrode charged to 50% state-of-charge in 0.5 h, we observed that the overwhelming majority of particles were either almost completely delithiated or lithiated. Specifically, only ∼2% of individual particles were at an intermediate state-of-charge. From this small fraction of particles that were actively undergoing delithiation, we conclude that the time needed to charge a particle is ∼1/50 the time needed to charge the entire particle ensemble. Surprisingly, we observed a very weak correlation between the sequence of delithiation and the particle size, contrary to the common expectation that smaller particles delithiate before larger ones. Our quantitative results unambiguously confirm the mosaic (particle-by-particle) pathway of intercalation and suggest that the rate-limiting process of charging is initiating the phase transformation by, for example, a nucleation-like event. Therefore, strategies for further enhancing the performance of LFP electrodes should not focus on increasing the phase-boundary velocity but on the rate of phase-transformation initiation.

LanguageEnglish (US)
Pages866-872
Number of pages7
JournalNano Letters
Volume13
Issue number3
DOIs
StatePublished - Mar 13 2013

Profile

Intercalation
intercalation
Electrodes
electrodes
Phase transitions
Phase boundaries
Lithium
Microscopic examination
Phosphates
Nucleation
Iron
Particle size
phase transformations
Transmission electron microscopy
X rays
Oxidation
lithium
LiFePO4
charging
electric batteries

Keywords

  • Lithium iron phosphate
  • mosaic
  • phase transformation
  • STXM
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

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

Cite this

Chueh, W. C., El Gabaly, F., Sugar, J. D., Bartelt, N. C., McDaniel, A. H., Fenton, K. R., ... McCarty, K. F. (2013). Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping. Nano Letters, 13(3), 866-872. DOI: 10.1021/nl3031899

Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping. / Chueh, William C.; El Gabaly, Farid; Sugar, Joshua D.; Bartelt, Norman C.; McDaniel, Anthony H.; Fenton, Kyle R.; Zavadil, Kevin R.; Tyliszczak, Tolek; Lai, Wei; McCarty, Kevin F.

In: Nano Letters, Vol. 13, No. 3, 13.03.2013, p. 866-872.

Research output: Contribution to journalArticle

Chueh, WC, El Gabaly, F, Sugar, JD, Bartelt, NC, McDaniel, AH, Fenton, KR, Zavadil, KR, Tyliszczak, T, Lai, W & McCarty, KF 2013, 'Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping' Nano Letters, vol 13, no. 3, pp. 866-872. DOI: 10.1021/nl3031899
Chueh WC, El Gabaly F, Sugar JD, Bartelt NC, McDaniel AH, Fenton KR et al. Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping. Nano Letters. 2013 Mar 13;13(3):866-872. Available from, DOI: 10.1021/nl3031899
Chueh, William C. ; El Gabaly, Farid ; Sugar, Joshua D. ; Bartelt, Norman C. ; McDaniel, Anthony H. ; Fenton, Kyle R. ; Zavadil, Kevin R. ; Tyliszczak, Tolek ; Lai, Wei ; McCarty, Kevin F./ Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping. In: Nano Letters. 2013 ; Vol. 13, No. 3. pp. 866-872
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abstract = "The intercalation pathway of lithium iron phosphate (LFP) in the positive electrode of a lithium-ion battery was probed at the ∼40 nm length scale using oxidation-state-sensitive X-ray microscopy. Combined with morphological observations of the same exact locations using transmission electron microscopy, we quantified the local state-of-charge of approximately 450 individual LFP particles over nearly the entire thickness of the porous electrode. With the electrode charged to 50{\%} state-of-charge in 0.5 h, we observed that the overwhelming majority of particles were either almost completely delithiated or lithiated. Specifically, only ∼2{\%} of individual particles were at an intermediate state-of-charge. From this small fraction of particles that were actively undergoing delithiation, we conclude that the time needed to charge a particle is ∼1/50 the time needed to charge the entire particle ensemble. Surprisingly, we observed a very weak correlation between the sequence of delithiation and the particle size, contrary to the common expectation that smaller particles delithiate before larger ones. Our quantitative results unambiguously confirm the mosaic (particle-by-particle) pathway of intercalation and suggest that the rate-limiting process of charging is initiating the phase transformation by, for example, a nucleation-like event. Therefore, strategies for further enhancing the performance of LFP electrodes should not focus on increasing the phase-boundary velocity but on the rate of phase-transformation initiation.",
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