| 摘要 |
PURPOSE:To satisfy practicability both in SD start temperature and resisting temperature by using in a battery separator a porous film made of polymer alloy wherein polyethylene (PE) and polypropylene (PP) are mixed at a specific ratio. CONSTITUTION:A separator is made of a porous film being mixture of PE and PP, which is formed of 10 to 90wt.% of PE and 90 to 10wt.% of PP. Thus if a temperature rises to a melting point of PE, only PE constituting the porous film is melted to have pores closed, and as a result an increase in a resistance value shuts current and prevents excessive rise in the temperature. Until a melting point of PP is reached, a film shape is maintained by PP being one of separator constituents and sufficient heat resisting temperature is exhibited. Thus shutdown (SD) start temperature is approximately 115 to 130 deg.C and the heat resisting temperature is approximately 150 deg.C or higher, so that practicability can be satisfied. |
