A preparation method of a polypropylene microporous membrane is provided, which comprises mixing polypropylene with a composite diluent to obtain a premix, wherein polypropylene accounts for 25 wt% to 60 wt% of the premix and the composite diluent accounts for 40 wt% to 75 wt% of the premix. The premix is subjected to melt extrusion and cooling molding, then the composite diluent is removed by an extractant, and then heat treatment is performed to obtain the polypropylene microporous membrane. The composite diluent comprises a high-temperature good solvent and a high-temperature poor solvent. The high-temperature good solvent is one or more selected from tetradecanol, hexadecanol, octadecanol and eicosanol, and the high-temperature poor solvent is one or more selected from benzyl alcohol, diphenyl carbonate, benzophenone and dimethyl sulfone. The high-temperature good solvent accounts for 30 wt% to 60 wt% of the composite diluent, and the high-temperature poor solvent accounts for 40 wt% to 70 wt% of the composite diluent. By adopting the specific composite diluent, the obtained polypropylene microporous membrane has uniform pore size distribution without macroporous defects, enhanced mechanical strength of the separator, and small difference in mechanical strength between the transverse and longitudinal directions, guaranteeing the safety performance of the separator and making it suitable as a lithium battery separator material.
Area Code: CN
Application Number: CN201910914867.0
