Measurement of the through thickness compression of a battery separator

The mechanical integrity of the separator is critical to the reliable operation of a battery. Due to its minimal thickness, compression experiments with a single/a few layers of separator are difficult to perform. In this work, a capacitance based displacement set-up has been developed for the measu...

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Bibliographic Details
Published in:Journal of power sources 2018-04, Vol.382, p.13-21
Main Authors: Yan, Shutian, Huang, Xiaosong, Xiao, Xinran
Format: Article
Language:English
Subjects:
Battery separator
Capacitance-displacement sensor
Thin film compression
Through thickness displacement
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Summary:The mechanical integrity of the separator is critical to the reliable operation of a battery. Due to its minimal thickness, compression experiments with a single/a few layers of separator are difficult to perform. In this work, a capacitance based displacement set-up has been developed for the measurement of the through thickness direction (TTD) compression stress-strain behavior of the separator and the investigation of its interaction with the electrode. The experiments were performed for a stack of two layers of Celgard 2400 separator, NMC cathode, and separator/NMC cathode/separator stack in both dry and wet (i.e. submersed in dimethyl carbonate DMC) conditions. The experimental results reveal that the separator compression modulus can be significantly affected by the presence of DMC. The iso-stress based rule of mixtures was used to compute the compressive stress-strain curve for the stack from that of the separator and NMC layer. The computed curve agreed with the experimental curve reasonably well up to about 0.16 strain but deviated significantly to a softer response at higher strains. The results suggest that, in the stack, the TTD compressive deformation of the separator is influenced by the NMC cathode. •A capacitance based displacement set-up has been developed for thin film testing.•The through thickness compression was measured for sample as thin as 50 μm.•PP separator, NMC cathode, and PP/NMC/PP stack were tested in air and in DMC.•PP separator shows a softer through thickness compressive response in DMC.•Response of the stack agreed with the rule of mixture prediction up to 0.16 strain.
ISSN:0378-7753
1873-2755
DOI:10.1016/j.jpowsour.2018.02.024