Multiscale Analysis and Safety Assessment of Fresh and Electrical Aged Lithium-Ion Pouch Cells Focusing on Mechanical Behavior

Marvin Sprenger*, Norbert Dölle, Florian Schauwecker, Marco Raffler, Christian Ellersdorfer, Wolfgang Sinz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Analyzing the impact of electrical aging on the lithium-ion cell’s mechanical behavior and safety is an important factor to assess the crash safety of electric vehicles during their lifetime. In this study, fresh and electrical aged state-of-the-art NCM pouch cells were investigated. Aged cells, which were cycled electrically to 90% state of health, under laboratory conditions in electric vehicle battery modules were used. The used charging/discharging strategy represents real customer behavior based on accelerated driving profiles. First, it is shown that electrical aging has a significant influence on the anodes’ and separators’ mechanical properties, which had a lower mechanical strength and stiffness under tension. Additionally, quasi-static cylindrical indentation and three-point bending tests were performed to investigate aging effects on cell level at varying state of charge (SOC). Aged cells with 0% SOC showed a right-shifted force–displacement curve and a 29% lower maximum force compared to fresh cells. Fully charged, aged cells reached a similar maximum force to fresh cells, but faster temperature increase and higher temperature peaks after internal short circuit. Inductively coupled plasma optical emission spectrometry analyses confirmed an increased lithium content on the anode surface, which is indicated in literature as a reason for the increased exothermic reaction of the aged cells. The results indicate a higher safety risk for the aged investigated pouch cells under mechanical loads based on their changed mechanical properties and thermal runaway behavior.

Original languageEnglish
Article number847
JournalEnergies
Volume15
Issue number3
DOIs
Publication statusPublished - 1 Feb 2022

Keywords

  • Crash safety
  • Electrical aging
  • Internal short circuit
  • Lithium plating
  • Lithium-ion battery
  • Mechanical properties change
  • Quasi-static indentation

ASJC Scopus subject areas

  • Control and Optimization
  • Energy (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering
  • Fuel Technology
  • Renewable Energy, Sustainability and the Environment

Fields of Expertise

  • Mobility & Production

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