Evolution of the Electrode-Electrolyte Interface of LiNi0.8Co0.15Al0.05O2 Electrodes Due to Electrochemical and Thermal Stress

Zachary W. Lebens-Higgins, Shawn Sallis, Nicholas V. Faenza, Fadwa Badway, Nathalie Pereira, David M. Halat, Matthew Wahila, Christoph Schlueter, Tien Lin Lee, Wanli Yang, Clare P. Grey, Glenn Amatucci, Louis F.J. Piper

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

For layered oxide cathodes, impedance growth and capacity fade related to reactions at the cathode-electrolyte interface (CEI) are particularly prevalent at high voltage and high temperatures. At a minimum, the CEI layer consists of Li2CO3, LiF, reduced (relative to the bulk) metal-ion species, and salt decomposition species, but conflicting reports exist regarding their progression during (dis)charging. Utilizing transport measurements in combination with X-ray and nuclear magnetic resonance spectroscopy techniques, we study the evolution of these CEI species as a function of electrochemical and thermal stress for LiNi0.8Co0.15Al0.05O2 (NCA) particle electrodes using a LiPF6 ethylene carbonate:dimethyl carbonate (1:1 volume ratio) electrolyte. Although initial surface metal reduction does correlate with surface Li2CO3 and LiF, these species are found to decompose upon charging and are absent above 4.25 V. While there is trace LiPF6 breakdown at room temperature above 4.25 V, thermal aggravation is found to strongly promote salt breakdown and contributes to surface degradation even at lower voltages (4.1 V). An interesting finding of our work was the partial reformation of LiF upon discharge, which warrants further consideration for understanding CEI stability during cycling.

Original languageEnglish (US)
Pages (from-to)958-969
Number of pages12
JournalChemistry of Materials
Volume30
Issue number3
DOIs
StatePublished - Feb 13 2018

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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