Lithium ion battery composite diaphragm and preparation method thereof

The invention provides a preparation method of a lithium ion battery composite diaphragm, which comprises the following steps: S1, grinding tencel chopped fibers by using grinding equipment to obtain slurry 1; s2, the pulp 1 passes through a screening-pulp grinding circulation system, and tencel fibrillated fibers with the maximum diameter smaller than 2.5 micrometers are obtained through screening; s3, polyester fibers, tencel fibrillated fibers and a PAE auxiliary agent are mixed uniformly and then fed into a fourdrinier to be dewatered and formed to obtain wet paper sheets, and the wet paper sheets are squeezed and dried in a Yankee cylinder to obtain dry paper sheets; s4, carrying out soft calendering treatment on the obtained dry paper sheet to obtain superfine fiber paper; s5, superfine fiber paper is atomized and wetted through water vapor and then compounded with the polyolefin microporous membrane through rolling, and then the compounded membrane is obtained after the compounded membrane and the poly