聚丙烯多孔膜是锂离子电池最常用的隔膜之一。隔膜孔结构的尺寸及其分布直接影响电池的使用和安全性能。聚丙烯隔膜的孔结构通过拉伸的方法制备，然而目前聚丙烯薄膜拉伸成孔机制尚不明确。针对该问题，本项目拟采用原位拉伸小角/广角X射线散射(SAXS/WAXS)跟踪拉伸过程中聚丙烯薄膜微观结构(包括孔结构的尺寸、尺寸分布,以及晶片厚度、晶体结构、分子取向等)的演化过程，明确聚丙烯微观结构对孔结构的影响及拉伸成孔的机制，为聚丙烯多孔隔膜孔结构的调控提供理论基础。.锂离子电池隔膜在使用过程中受到温度、压力、溶剂等环境的影响。明确在多重外部环境下孔结构演化过程及隔膜稳定性能对于锂离子电池的安全性能具有十分重要的意义。针对环境对隔膜的影响，本项目拟采用原位SAXS/WAXS跟踪隔膜微观结构在多重环境下的演化过程，明确多重环境耦合作用下微孔的演化机制，为提高锂离子电池隔膜的安全性能提供理论基础。

The separator, which is generally made by porous polypropylene membrane, is one of the most important components of lithium ion battery. The size and size distribution of pores determine the internal resistance and also the safety of the battery. The pores are prepared by uniaxial or biaxial stretch, where the microscopic mechanism of the stretch induced cavitation in polypropylene still remains obscure. Therefore, one of the major objects of this work is to study the mechanism of the stretch induced cavitation in polypropylene film. The microstructure evolutions during the stretch, such as pore size, size distribution, crystalline lamellar thickness, crystallinity, crystallographic etc. will be tracked by in situ SAXS and WAXS, in order to understand the relationship between microstructure and the cavitation behavior. The results will promote the understanding of the cavitation behavior of polypropylene during stretch and provide the theoretic basic for the controlling of size distribution during the processing of the porous polypropylene membranes. .The separator is under effects of the temperature, pressure and solvent etc. in the lithium ion battery. It is very important to study the mechanism of the evolution of the porous structure in the separator under different external environments. In order to understand the real time structure changes of the separator in lithium ion battery, an environmental simulation device for SAXS and WAXS experiment will be designed and established. In situ SAXS/WAXS will be used to study the structural evolution of the separator under multiple external environments with the help of the environmental simulation device. This work will provide theory fundamentals for the safety improvement of lithium ion batteries.