METHOD OF MAKING MEMBRANE HAVING MICROSCOPIC HOLES DIFFERS IN SIZE TO DIRECTION OF THICKNESS

摘要

PURPOSE: A method of making membrane is provided to increase the stability of membrane as an isolation membrane of battery cell and improve the shut down function. CONSTITUTION: The method of membrane making comprises the step of projecting the high energy ions on the surface of a high polymer membrane in a vacuum circumstance to form microscopic hole in the membrane. In the membrane, the size of microscopic hole is decreasing with the advance of distance from the surface of membrane. The method improves the shut down function of membrane caused by the dispersion and size of the microscopic hole and make a membrane of better mechanical property with less physical damage without contamination to circumstance.