Aging of tesla's 18650 lithium-ion cells: Correlating solid-electrolyte-interphase evolution with fading in capacity and power

M. Uitz*, M. Sternad, S. Breuer, C. Täubert, T. Traußnig, V. Hennige, I. Hanzu, M. Wilkening

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The long-term performance of commercial lithium-ion batteries used in today's electric vehicles is of utmost importance for automotive requirements. Here, we use Tesla's 18650 cells manufactured by Panasonic to elucidate the origins of capacity fading and impedance increase during both calendar and cycle aging. Full cell testing is systematically carried out at three different temperatures (25°C, 40°C, 60°C). The cells are galvanostatically cycled at different C-rates (0.33 C - 1 C) and calendar aging is monitored at 4 different state-of-charges (SOC). Operation at high temperatures turns out to have the largest effect on both the capacity and direct current (DC) impedance. As an example, after 500 cycles at 25°C and 40°C capacity fading is approximately 12%, while at 60°C the fading reaches 22%. Our DC impedance measurements reveal the same trend. Post mortem analysis indicate that aging is strongly related to changes of the solid electrolyte interphase (SEI). Hence, the changes in performance are correlated with the change in composition (and thickness) of the SEI formed. In particular, we quantitatively measure the formation of electrically insulating LiF and find a correlation between overall DC impedance of the cells and lithium fluoride of the SEI.

Original languageEnglish
Pages (from-to)A3503-A3510
JournalJournal of the Electrochemical Society
Volume164
Issue number14
DOIs
Publication statusPublished - 2017

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

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