Cycle aging of commercial NMC/graphite pouch cells at different temperatures

K. Jalkanen, J. Karppinen, L. Skogström, T. Laurila, M. Nisula, K. Vuorilehto*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

126 Citations (Scopus)

Abstract

Cycle aging of commercial 40. A. h pouch-type lithium-ion cells with NMC/graphite chemistry was studied at different cycling temperatures (room temperature, +45. °C, and +45. °C charge/+65. °C discharge). Aging was observed as capacity fade and resistance increase, and the aging mechanisms were characterized by electrochemical impedance spectroscopy and post-mortem analysis, where visual inspection and thickness measurements were employed together with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses. It was observed that elevated temperatures resulted in accelerated capacity fade, especially for the +45. °C/+65. °C condition. SEI-layer growth and lithium plating, discovered in cell disassembly, were attributed to be the main mechanisms responsible for capacity loss. In addition to the capacity fade, resistance increase was observed both in ohmic and polarization resistances. The ohmic resistance growth was attributed to lack of electrolyte and increased separator resistance. Polarization resistance evolution during cycling was similar at room temperature and at +45. °C, but different at the +45. °C/+65. °C condition. It was concluded that post-mortem analysis is essential for attributing the cycle testing and impedance spectroscopy results to different components and processes inside the cell. For example, the lithium plating phenomenon could not have been predicted or discovered without disassembling the cells.

Original languageEnglish
Pages (from-to)160-172
Number of pages13
JournalApplied Energy
Volume154
Issue number9
DOIs
Publication statusPublished - 5 Sep 2015
MoE publication typeA1 Journal article-refereed

Keywords

  • Aging mechanisms
  • Commercial pouch cell
  • Cycle aging
  • Lithium plating
  • Lithium-ion battery lifetime
  • Post-mortem analysis

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