Polyethylene microporous membrane and preparation method thereof, and diaphragm for lithium ion battery

The invention relates to a preparation method of a polyethylene microporous membrane. The preparation method comprises the following steps: subjecting ultrahigh-molecular-weight polyethylene particles and a pore-forming agent to premixing, feeding, melt extrusion and cooling to obtain a substrate, wherein the ultrahigh-molecular-weight polyethylene particles are prepared from polyethylene with a weight-average molecular weight of 1.2 million g/mol to 1.5 million g/mol; carrying out stretching treatment on the substrate by adopting a two-way synchronous stretching process with a stretching ratio of 8 * 8 to 10 * 10 so as to obtain an oil film; and sequentially extracting and shaping the oil film to obtain the polyethylene microporous film. The invention further relates to a diaphragm for the quick-charge lithium ion battery. The diaphragm comprises the polyethylene microporous membrane prepared by the preparation method. 本发明涉及一种聚乙烯微孔膜的制备方法，包括以下步骤：将超高分子量聚乙烯颗粒和成孔剂经预混、喂料、熔融挤出、冷却，得到基片，所述超高分子量聚乙烯颗粒由重均分子量为120万g/mol～