| CPC H01M 10/0569 (2013.01) [H01M 50/417 (2021.01); H01M 50/451 (2021.01); H01M 50/457 (2021.01); H01M 50/489 (2021.01); H01M 50/491 (2021.01); H01M 50/494 (2021.01); H01M 2300/0028 (2013.01)] | 12 Claims |

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1. A trilayer microporous battery separator which comprises a microporous film, the microporous film having a polypropylene/polyethylene/polypropylene layer structure having a layer thickness ratio of 31%/38%/31%; having a thickness from 12 to 17 microns, having an average lamellae thickness of 132 nm, and a maximum lamellae thickness between 153 and 195 nm, a swelling in DEC of 0.7% or less, unrestrained MD shrinkage, when the microporous film is baked unrestrained at 90° C. for 1 hour, of more than 5%, an unrestrained MD shrinkage, when the microporous film is baked unrestrained at 105° C. for 1 hour, of 9% or more, and having at least one property selected from the group consisting of:
MD restrained growth of less than or equal to 0.2%;
rebound of 5% or greater;
a max compression greater than or equal to 18%;
the microporous film exhibits a round-shaped opening having a length equal to a height of the opening when subjected to a puncture test;
a normalized puncture strength above 350 gf/16 micron; and
wherein the lamellae are structures extending between pores in the microporous film.
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