Abstract: Conventional separators had a function that their melting made minute holes inside the separator smaller, leading to cut off of ion conductivity in temperature increase due to unusual conditions such as short circuit. However, there was a problem that, at a temperature higher than a certain degree, not only the minute holes were closed but also the separator itself was melted to cause deformation of the separator such as shrink and generation of holes due to melting and insulation was broken. The present invention has been carried out in order to solve the above problems. The separator for batteries of the present invention comprises a first porous layer (3a) containing a thermoplastic resin as a main component and a second porous layer (3b) laminated on the first porous layer (3a), which has higher heat resistance than that of the first porous layer (3a).

Abstract: As to the batteries containing an organic low molecular compound in the space between the positive and negative electrodes, there has been a risk of unusual conditions such as ignition because the organic low molecular compound in liquid was released from the above space to the outside, when there was heating of the battery and the like.

Abstract: Conventional separators had a function that their melting made minute holes inside the separator smaller, leading to cut off of ion conductivity in temperature increase due to unusual conditions such as short circuit. However, there was a problem that, at a temperature higher than a certain degree, not only the minute holes were closed but also the separator itself was melted to cause deformation of the separator such as shrink and generation of holes due to melting and insulation was broken.