| abstract |
A thin polyolefin microporous membrane having a high porosity and excellent permeability and mechanical strength, a battery separator using such a microporous membrane, and a battery using such a separator are provided. SOLUTION: In a pore size distribution curve obtained by mercury porosimetry, a pore volume having a pore radius in the range of 100 to 1,000 nm is compared with a pore volume S 1 having a pore radius in the range of 10 to 1,000 nm. and the S ratio of 2 (S 2 / S 1 × 100) is 25% or more, and the ratio of the pore volume S 3 range pore radius of 500~1,000nm (S 3 / S 1 × 100) is A polyolefin microporous membrane of 5% or less. [Selection] Figure 1 |