LAMINATED MICROPOROUS MEMBRANE AND PREPARATION METHOD THEREOF

摘要

PURPOSE: A laminated microporous membrane, its preparation method and a lithium ion secondary battery or lithium ion polymer secondary battery containing the membrane as a separation membrane are provided, to lower the shutdown temperature and to improve the melt integrity without deterioration of the permeability of the membrane. CONSTITUTION: The laminated microporous membrane comprises a polymer supporting layer; a shutdown layer prepared by coating the one or both sides of the supporting layer with a polymer having a melting point lower than that of the polymer of the supporting layer. Preferably the difference of the melting points of the two polymers is 40-75 deg.C. Preferably the supporting layer has a pore size of 0.001-100 micrometers and a thickness of 1-50 micrometers; and the shutdown layer has a pore size of 0.001-100 micrometers and a thickness of 0.01-20 micrometers. The method comprises the steps of making the supporting layer; coating the one or both sides of the supporting layer with the polymer solution of a polymer having a melting point lower than that of the polymer of the supporting layer; and drying the coated layer, or dipping the coated layer into a solvent and drying it to prepare the shutdown layer by the phase separation.