The compression behavior, microstructure evolution and properties variation of three kinds of commercial battery separators under compression load

Abstract

In this article, the compression behavior, microstructure evolution and properties variation of three kinds of commercial polyolefin separator under compression load are systematically analyzed. The compression testing shows that three kinds of separators present two different deformation modes. The separator made from dry process by uniaxial stretching has good resistance to compression load due to the parallel lamellae aligned along thickness direction on cross-section. And all properties variation with stress display striking uniformities with compression curves. While the other two separators with biaxial stretching, both dry and wet process, have abundant multilayered structure, causing weaker resistance to compression load and flatter compression curves. And all properties show gentle trend for biaxial stretching separator. However, three kinds of separators also share some common characteristics. The separators compact violently along thickness direction under lower strain firstly, accompanied by the dramatic decline of porosity but slightly change connectivity along thickness direction. And subsequently the connectivity along thickness direction is severely destroyed at higher strain due to different reasons. The violent shear or glide of microporous structure occurs perpendicular to thickness direction for separator with uniaxial stretching and micropores direct blocking by non-corresponding micropores position between multilayered structure for separator with biaxial stretching.