Microporous structure and mechanical behavior of separators used for lithium-ion battery

Abstract

Three most commonly used commercial polymer separators are selected to investigate the relationship between microstructure and performance of lithium-ion battery separators. The mechanical behavior and failure modes of separators in all probable loading conditions are compared. The scanning electron microscopy, two-dimensional wide-angle X-ray diffraction, and various performance tests show that the separator prepared by the dry process with uniaxial stretching has high anisotropy. Consequently, the tensile strength varies greatly in different directions, the puncture strength is also the lowest. But the parallel arranged lamellae on cross-section act as the support structure for separator, causing better compression resistance and weak delamination trends. While the separators produced by the dry process with biaxial stretching and wet process have comparable strength levels when stretched in different directions and higher puncture strength. But the biaxial stretching leads to the stacked multilayer structure with poor connection or support structure along the thickness direction, causing a weaker compression resistance but stronger delamination trend.