Asahi Kasei Battery Separator Corporation

Kosuke Mizobuchi

Xun Zhang

Yuzuru Sakakibara

Yuka Sato

Provided is a microporous film which has a surface A and a surface B opposite to the surface A. In one embodiment, the microporous film has a ratio (F/F) of a dynamic friction coefficient Fof the surface B to a dynamic friction coefficient Fof the surface A of 1.2 to 20. In another embodiment, the microporous film is a single layer having a thickness of 3-18 μm, a number Nof pores on the surface A is 10-100/μm, a number Nof pores on the surface B is 20-200/μm, and N/Nis 0.2-0.96. In addition, a total area Sof pores on the surface A is 0.02-0.5 μm/μm, a total area Sof pores on the surface B is 0.01-0.3 μm/μm, and S/Sis 1.1-10. Furthermore, in another embodiment, a number Wof protrusion-like bodies on the surface B is 0.2-1000/100 μm.

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Tokyo, Japan

Kosuke Mizobuchi