| 摘要 |
PROBLEM TO BE SOLVED: To provide a separator for liquid-type lead storage batteries, which allows a dendrite short circuit to be prevented as far as possible even when used in an environment that can easily bring a battery into the state of being overdischarged, in which the separator is composed of a ribbed microporous film having an average pore diameter of about 0.02-0.2 μm, a maximum pore diameter of about 0.3-0.8 μm, and a porosity of about 55-75%, which has been regarded as being less prone to causing a dendrite short circuit in a liquid-type lead storage battery conventionally.SOLUTION: A separator for liquid-type lead storage batteries is composed of a ribbed microporous film arranged by: melting and kneading a raw material composition chiefly including a polyolefin-based resin, inorganic powder and a plasticizer; integrally molding into a film-like form having a tabular sheet and main ribs provided on one side of the tabular sheet so as to protrude for abutting against an electrode plate; and then, removing part of the plasticizer. The ribbed microporous film has mini-ribs for abutting against an electrode plate provided on a face of the tabular sheet on the side opposite to the one side of the tabular sheet where the main ribs are provided. The mini-ribs each have a height less than 0.3 times that of the main rib in height, and a bottom rib width less than 0.3 times that of the main rib. |
