| 摘要 |
PROBLEM TO BE SOLVED: To provide a separator for a nonaqueous electrolyte secondary battery not allowing large deformation, and having a shutdown function, when there is heat-generation caused by an inner or outer short circuit. SOLUTION: This separator for a nonaqueous electrolyte secondary battery includes both a porous film having a shutdown function and a porous layer made of a heat-resistant resin, while a dimensional change of the separator measured by thermomechanical analysis is from -5% to +5%. The dimensional change measured by the thermomechanical analysis is defined by the following expression: (Lmax-L25)/L25)×100[%], when a temperature of the separator of 4 mm width and 20 mm length is increased at the constant speed 10 deg.C/min. in a state such that the separator is longitudinally pulled under the constant load 5g, wherein L25 is a separator length [mm] at 25 deg.C, and Lmax is a 1ength [mm] when the separator is maximumly extended or contracted up to 200 deg.C. |
