Probing the roles of polymeric separators in lithium-ion battery capacity fade at elevated temperatures

Jianchao Chen, Yongda Yan, Tao Sun, Yue Qi, Xiaodong Li

    Research output: Research - peer-reviewArticle

    • 6 Citations

    Abstract

    The high temperature mechanical property of separators is very important for safety of lithium-ion batteries. However, the mechanical integrity of polymeric separators in lithium-ion batteries at elevated temperatures is still not well characterized. In this paper, the temperature dependent micro-scale morphology change of PP (polypropylene)-PE (polyethylene)-PP sandwiched separators (Celgard 2325) was studied by in-situ high temperature surface imaging using an atomic force microscope (AFM) coupled with power spectral density (PSD) analysis and digital image correlation (DIC) technique. Both PSD and DIC analysis results show that the PP phase significantly closes its pores by means of dilation of the nanofibrils surrounding the pores in the transverse direction and shrinkage in the machine direction, when cycled at 90°C, even below the separator's shutdown temperature (∼120°C) and its own melting temperature (165°C). This is presumably due to surface melting effect in nanostructures and should be size dependent-the surface melting temperature may decrease with the diameter of nanofibrils. Therefore, some pore closing might happen even at operating temperatures, it will lead to capacity fade that is undesired for battery performance.

    LanguageEnglish (US)
    JournalJournal of the Electrochemical Society
    Volume161
    Issue number9
    DOIs
    StatePublished - 2014

    Profile

    separators
    electric batteries
    lithium
    ions
    temperature
    Separators
    Temperature
    Lithium-ion batteries
    polypropylene
    melting
    porosity
    Polypropylenes
    Power spectral density
    Melting point
    Direction compound
    shutdowns
    closing
    operating temperature
    shrinkage
    integrity

    ASJC Scopus subject areas

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

    Cite this

    Probing the roles of polymeric separators in lithium-ion battery capacity fade at elevated temperatures. / Chen, Jianchao; Yan, Yongda; Sun, Tao; Qi, Yue; Li, Xiaodong.

    In: Journal of the Electrochemical Society, Vol. 161, No. 9, 2014.

    Research output: Research - peer-reviewArticle

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    abstract = "The high temperature mechanical property of separators is very important for safety of lithium-ion batteries. However, the mechanical integrity of polymeric separators in lithium-ion batteries at elevated temperatures is still not well characterized. In this paper, the temperature dependent micro-scale morphology change of PP (polypropylene)-PE (polyethylene)-PP sandwiched separators (Celgard 2325) was studied by in-situ high temperature surface imaging using an atomic force microscope (AFM) coupled with power spectral density (PSD) analysis and digital image correlation (DIC) technique. Both PSD and DIC analysis results show that the PP phase significantly closes its pores by means of dilation of the nanofibrils surrounding the pores in the transverse direction and shrinkage in the machine direction, when cycled at 90°C, even below the separator's shutdown temperature (∼120°C) and its own melting temperature (165°C). This is presumably due to surface melting effect in nanostructures and should be size dependent-the surface melting temperature may decrease with the diameter of nanofibrils. Therefore, some pore closing might happen even at operating temperatures, it will lead to capacity fade that is undesired for battery performance.",
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    AU - Sun,Tao

    AU - Qi,Yue

    AU - Li,Xiaodong

    PY - 2014

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    N2 - The high temperature mechanical property of separators is very important for safety of lithium-ion batteries. However, the mechanical integrity of polymeric separators in lithium-ion batteries at elevated temperatures is still not well characterized. In this paper, the temperature dependent micro-scale morphology change of PP (polypropylene)-PE (polyethylene)-PP sandwiched separators (Celgard 2325) was studied by in-situ high temperature surface imaging using an atomic force microscope (AFM) coupled with power spectral density (PSD) analysis and digital image correlation (DIC) technique. Both PSD and DIC analysis results show that the PP phase significantly closes its pores by means of dilation of the nanofibrils surrounding the pores in the transverse direction and shrinkage in the machine direction, when cycled at 90°C, even below the separator's shutdown temperature (∼120°C) and its own melting temperature (165°C). This is presumably due to surface melting effect in nanostructures and should be size dependent-the surface melting temperature may decrease with the diameter of nanofibrils. Therefore, some pore closing might happen even at operating temperatures, it will lead to capacity fade that is undesired for battery performance.

    AB - The high temperature mechanical property of separators is very important for safety of lithium-ion batteries. However, the mechanical integrity of polymeric separators in lithium-ion batteries at elevated temperatures is still not well characterized. In this paper, the temperature dependent micro-scale morphology change of PP (polypropylene)-PE (polyethylene)-PP sandwiched separators (Celgard 2325) was studied by in-situ high temperature surface imaging using an atomic force microscope (AFM) coupled with power spectral density (PSD) analysis and digital image correlation (DIC) technique. Both PSD and DIC analysis results show that the PP phase significantly closes its pores by means of dilation of the nanofibrils surrounding the pores in the transverse direction and shrinkage in the machine direction, when cycled at 90°C, even below the separator's shutdown temperature (∼120°C) and its own melting temperature (165°C). This is presumably due to surface melting effect in nanostructures and should be size dependent-the surface melting temperature may decrease with the diameter of nanofibrils. Therefore, some pore closing might happen even at operating temperatures, it will lead to capacity fade that is undesired for battery performance.

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