A lithium ion battery separator and preparation method nanofiber

The invention relates to a composite nanometer fiber lithium ion battery diaphragm and a preparation method thereof. The battery diaphragm is formed by compounding a layer of polymer nanometer fiber films on the surface of a polyolefin microporous film, the fiber film consists of fiber yarns, the battery diaphragm has the thickness being 20 to 60mum, the vertical shrinkage factor is smaller than 1 percent, the porosity is 35 to 70 percent, and the diameter of the fiber yarns is 3nm to 4mum. The composite nanometer fiber lithium ion battery diaphragm has the advantages that the performance is excellent, good wettability, permeability and temperature resistance are realized, in addition, the interface property between the battery diaphragm and positive and negative electrode materials is improved, and the safety and the circulation performance of the battery are improved.