Effects of Polypropylene Orientation on Mechanical and Heat Seal Properties of Polymer-Aluminum-Polymer Composite Films for Pouch Lithium-Ion Batteries

The results revealed that in the PA-Al-PP composite film, the PA layer with the highest tensile strength can release a large amount of tensile stress from the Al layer during stretching, while the PP layer with the lowest tensile strength can restrain the further development of the small cracks on the boundary of the Al layer under tensile stress; in this way, the high tensile strength and plastic deformation of the composite film are obtained

Fangxinyu Zeng

2018

Scholarcy highlights

  • Compared to other commonly used rechargeable batteries, the lithium ion batteries are featured by higher energy density, higher cell voltage, less memory effect, very good cycle life, light weight, environmental friendliness and have found wide application in the area of communication and portable instruments
  • The results revealed that in the PA-Al-PP composite film, the PA layer with the highest tensile strength can release a large amount of tensile stress from the Al layer during stretching, while the PP layer with the lowest tensile strength can restrain the further development of the small cracks on the boundary of the Al layer under tensile stress; in this way, the high tensile strength and plastic deformation of the composite film are obtained
  • Two PP layers with different orientation status were used to prepare the laminated films to explore the role of PP orientation in the peeling and tensile behavior of heat seal strength of the laminated film
  • The results revealed that the orientation status of the PP layer has little influence on the peeling force of the sample; it influences the slope of the peeling curve
  • From the aspect of the PP layer orientation, it was found that in the case of the PP layer without orientation, its HSS in machine direction and transverse direction are quite similar; while in the case of PP with orientation, a significant difference in heat seal behavior in MD and TD was found: in MD, the composite film exhibit higher HSS, lower Tcrit and less time to achieve high HSS, while in TD, lower HSS, higher Tcrit and more time to obtain high HSS were observed; the related mechanism was proposed based on the oriented molecules in the PP layer
  • The results in this study elucidated that for the PP-Al-PA composite film, only if the tensile stress was released by each layer efficiently during the HSS measurement could the composite film exhibit the desired high HSS that was even higher than its tensile strength
  • Adequate lamination of each layer is very important for the final properties of the film

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