A 3D image-based modelling method is developed to predict compressive behaviour of Li-ion battery (LIB) separators. The separator sample of LIB, consisting of polypropylene (PP) matrix and pores, is imaged using nanoscale X-ray computed tomography (XCT). The microstructure of the solid PP phase is obtained by the segmentation of the image. The segmented microstructures are used to characterise the geometrical properties of LIB separators, including porosity and tortuosity, which are important parameters for characterizing the performance of separator related to the transport of Li-ion through the separator. A 3D finite element model based on the microstructure of separator is established for the study of the compressive behaviour of separator from micro-scale. Due to the limitation of relatively low resolution of nanoscale XCT (∼100 nm), the fibrils (< 100 nm) of polymer separator cannot be captured in the image-based model. A method is proposed to add fibrils into the image-based model, which is validated using experimental stress-strain curves and the images obtained from scanning electronic microscope (SEM). Finally, the porosity and tortuosity of LIB separator under compression are determined analytically to obtain a relationship between tortuosity and porosity of the separator, which can be used to analyse the performance of LIB with deformed separators.

开发了一种基于 3D 图像的建模方法来预测锂离子电池 (LIB) 隔膜的压缩行为。LIB 的隔膜样品由聚丙烯 (PP) 基质和孔组成，使用纳米级 X 射线计算机断层扫描 (XCT) 成像。通过图像的分割获得固体PP相的微观结构。分段的微结构用于表征 LIB 隔膜的几何特性，包括孔隙率和曲率，这是表征与锂离子通过隔膜传输相关的隔膜性能的重要参数。建立了基于隔板微观结构的3D有限元模型，从微观尺度研究隔板的压缩行为。由于纳米级 XCT（~100 nm）分辨率相对较低的限制，在基于图像的模型中无法捕获聚合物隔膜的原纤维 (< 100 nm)。提出了一种将原纤维添加到基于图像的模型中的方法，该方法使用实验应力-应变曲线和从扫描电子显微镜 (SEM) 获得的图像进行验证。最后，通过解析确定LIB隔膜在压缩下的孔隙率和弯曲度，得到隔膜弯曲度和孔隙率之间的关系，可用于分析LIB与变形隔膜的性能。