| 摘要 |
<p>The present invention relates a microporous polyethylene film with improved mechanical strength, porosity, pore size and, particularly, improved surface energy, thereby having improved electrolyte wettability and being adequate for use as separators in high-capacity and long lifetime lithium secondary batteries. The microporous polyethylene film of the present invention is characterized by having a surface energy of at least 50 dynes/cm 2 , an air permeability (Darcy's permeability constant) of at least 2.0x10 -5 , a puncture strength of at least 0.17 N/m, a product of the air permeability and the puncture strength of at least 0.34x10 -5 Darcy N/m, a weighted average pore size of at least 30 nm, and a film shrinkage in the transverse and machine directions of not more than 5% at 105 °C for 10 minutes and not more than 15% at 120 °C for 60 minutes, respectively. The microporous polyethylene film is prepared by compounding raw materials in an extruder such that a thermodynamic single phase is formed above the temperature of liquid-liquid phase separation, inducing sufficient phase separation in a phase separation zone formed inside the extruder by controlling the temperature below the temperature of liquid-liquid phase separation, forming through a die, and carrying out plasma treatment in order to enhance surface energy.</p> |
