Thermomechanical analysis and durability of commercial micro-porous polymer Li-ion battery separators

Love, Corey T.

doi:10.1016/j.jpowsour.2010.10.083

Cited by 145 publications

(92 citation statements)

References 16 publications

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“…It is observed that, while water did not change the mechanical properties of the PP separators, the presence of electrolyte with or without lithium salt softened the PP separator by~50%. This softening effect was not observed in the measurement with pre-wet samples [14]. In other words, the softening behavior of the PP separator occurred only when it was immersed in certain solutions and the solutions did not irreversibly alter the mechanical property of the PP separator.…”

Section: Introductionmentioning

confidence: 71%

Unveiling the environment-dependent mechanical properties of porous polypropylene separators

Yan

Xiao

Huang

et al. 2014

Polymer

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a b s t r a c tPorous polypropylene (PP) is commonly used as separator materials for lithium ion batteries (LIB). Its mechanical properties, especially critical for abuse tolerance and durability of LIB, are subject to change in different environments. To capture the mechanical responses of a porous PP separator, its microstructure was mapped into separate atomistic models of bulk crystalline phases and oriented amorphous nanofibers. These structures were relaxed and stretched in vacuum, water, and dimethyl carbonate (DMC) using molecular dynamics (MD). The simulation results revealed DMC molecules penetrated into the amorphous PP nanofiber, and reduced the local density and the Young's modulus. In contrast, water increased the Young's modulus of the amorphous PP nanofiber. Furthermore, neither water nor DMC had any impact on the Young's modulus of the crystalline phase. These results suggest that the DMC induced separator softening was attributed to the strong attraction of the less-polar DMC solvent with the amorphous fibrous PP nanofibers.

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Section: Introductionmentioning

confidence: 71%

Unveiling the environment-dependent mechanical properties of porous polypropylene separators

Yan

Xiao

Huang

et al. 2014

Polymer

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“…These tensile stress-strain curves are qualitatively similar to those presented in previous work investigating the tensile properties of microporous Celgard separators. [11][12][13][14] The tensile mechanical behavior of all of the tested separators is summarized in Figs. 7 and 8, which show effective modulus and flow stress at different strain rates for separators tested in the machine and transverse direction, respectively.…”

Section: Resultsmentioning

confidence: 99%

Mechanical Properties of a Battery Separator under Compression and Tension

Cannarella

Liu

Leng

et al. 2014

J. Electrochem. Soc.

195

143

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Knowledge of the compressive mechanical properties of battery separator membranes is important for understanding their long term performance in battery cells where they are placed under compression. This paper presents a straightforward procedure for measuring the compressive mechanical properties of battery separator membranes using a universal compression testing machine. The compressive mechanical properties of a microporous polypropylene separator are characterized over a range of strain rates and in different fluid environments. These measurements are then compared to measurements of the rate and fluid-dependent mechanical properties of the separator under tension. High strain rate dependence due to viscoelasticity is observed in both tension and compression. An additional rate dependence due to poroelastic effects is observed in compression at high strain rates. A reduction in mechanical properties is observed in DMC solvent environments for both tension and compression, but is found to be less pronounced in compression. The difference in mechanical properties between compression and tension highlight the anisotropic nature of battery separators and the importance of measuring compressive properties in addition to tensile properties. The battery separator is a porous polymer membrane used to create a physical barrier between electrodes in a battery cell. The separator must be mechanically robust to ensure safe operation over the cell's service life: mechanical failure leading to electrode contact can result in catastrophic failure of the cell.1-3 Such failure often follows from puncture or thermal shrinkage of the membrane.4-6 Non-catastrophic battery failure through the form of accelerated degradation can also result from separator deformation. [7][8][9] The importance of the mechanical properties of the separator with respect to battery safety and durability has consequently motivated much research on the mechanical properties of battery separators.Previous works on the mechanical properties of separator have mainly investigated the mechanical properties under tension. [10][11][12][13][14] While knowledge of the tensile properties of the separator are important from a manufacturing standpoint, where the separator is placed under tension during cell assembly, the tensile properties are less relevant for general battery operation. This is because the separator is placed under compression during typical battery operating conditions, where it is compressed in the direction normal to the plane of the large separator face by the anode and cathode. This compressive stress is cyclic owing to reversible electrode strains and gradually increases during operation as a result of irreversible volumetric increases occurring on the electrodes. 9,15 These stack stresses during operation have been observed to be on the order of 1MPa in previous work, 9,15,16 although the presence of geometric non-uniformities (e.g. particles and curved faces) can result in local stresses that are significantly higher. 17-19The mechanical...

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“…In [25]. When using liquid electrolyte in the battery, softening and shrinkage of the polyolefin separator that occurs at elevated temperature above 90 °C (i.e., above the mechanical  relaxation peak) can result in closure of the pores and further lower the ionic conductivity [26]. However, such problem can be greatly alleviated by replacing the liquid electrolyte soaked separator with our solvent-free PEM.…”

Section: Thermal Stability Of Pemmentioning

confidence: 99%

Highly conductive solvent-free polymer electrolyte membrane for lithium-ion batteries: Effect of prepolymer molecular weight

Echeverri

Ward

et al. 2016

Journal of Membrane Science

110

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Thermomechanical analysis and durability of commercial micro-porous polymer Li-ion battery separators

Cited by 145 publications

References 16 publications

Unveiling the environment-dependent mechanical properties of porous polypropylene separators

Unveiling the environment-dependent mechanical properties of porous polypropylene separators

Mechanical Properties of a Battery Separator under Compression and Tension

Highly conductive solvent-free polymer electrolyte membrane for lithium-ion batteries: Effect of prepolymer molecular weight

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