Dynamic In-Plane Heterogeneous and Inverted Response of Graphite to Fast Charging and Discharging Conditions in Lithium-Ion Pouch Cells

Abigale Monasterial, Peter Weddle, Kristen Atkinson, David Wragg, Andrew Colclasure, Francois Usseglio-Viretta, Natalie Seitzman, Jun-Sang Park, Jonathan Almer, Kandler Smith, Donal Finegan

Research output: Contribution to journalArticlepeer-review

Abstract

Solutions for improving fast charging of lithium-ion batteries have largely focused on alleviating through-plane lithiation gradients while little is understood about in-plane heterogeneities and how to resolve them. Herein, high-speed synchrotron X-ray diffraction (XRD) resolves graphite lithiation spatially and temporally during 6 C charging and 2 C discharging. At every point during operation, considerable differences in the state of lithiation across the pouch cell are present. Some regions are more responsive to operation than others, reaching full lithiation early during charge and full delithiation during discharge. Other regions within the cell never fully delithiate during discharge, despite a prolonged voltage hold at 2.8 V. Using time-resolved XRD data, the calculated local current density (mA cm−2) at the graphite surface shows an unexpected occurrence of local inverted current densities where regions of graphite are observed to delithiate during charging and lithiate during discharging. A pseudo-3D model is developed for the graphite electrode with spatially varying microstructural tortuosity to show how microstructural heterogeneity could influence spatial charge dynamics. The model could not predict the complex in-plane charge behavior observed within the cell. Consequently physics-based charging protocols based on homogeneous electrode assumptions may underestimate the local variations in charge dynamics and occurrence of lithium plating.

Original languageAmerican English
Article number2200067
Number of pages14
JournalSmall Science
Volume3
Issue number7
DOIs
StatePublished - 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Small Science published by Wiley-VCH GmbH.

NREL Publication Number

  • NREL/JA-5700-86256

Keywords

  • fast charging
  • heterogeneity
  • Li-ion battery
  • modeling
  • X-ray diffraction

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