| 摘要 |
The invention relates to a microporous membrane, which is provided with high safety even under a condition that the interior temperature of a battery becomes high, and which has high permeability and high mechanical strength at the same time. The polyolefin microporous membrane is characterized by a membrane thickness of 5 to 50 mum, a void content of 30 to 60%, a gas transmission rate of 40 to 300 sec/100 cc/20 mum, a piercing strength of not less than 2.5 N/20 mum and a break through temperature of not lower than 110° C. The separator in accordance with the present invention is used to exhibit high safety under a high temperature condition as well as high permeability, and therefore it is particularly useful as a separator for miniaturized high capacity batteries of a non-aqueous electrolytic solution type.
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