Preparation of micro-porous polyethylene membrane by 2-component melt-process

A separator for lithium ion secondary battery was made by PE-solvent 2-component melt process. The relationship between phase separation and membrane morphology was examined. The effects of extension on the morphology of the membrane was also examined. In liquid-liquid phase separation, cell structures were found in the membrane. The cell diameter increased with slower cooling and with decrease in alkyl chain length in dialkyl phthalates. In solid-liquid phase separation, no cell structures were found. After phase separation, extension and extraction of the solvent were carried out. The puncture strength increased with extension.