High-strength separator
AssigneeAsahi Kasei Battery Separator Corporation
InventorsXun Zhang, Ryo Kuroki, Yuichiro Ido, Kensuke Niimura, Tomoki Ishikawa
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Abstract
A separator for an electricity storage device has a cross-sectional crystal orientation of 0.85 or greater, and/or a method for producing the separator for an electricity storage device comprises a step of using a continuous mixer under conditions with a temperature of 20° C. to 70° C., a shear rate of 100 to 400,000 seconds−1 and a residence time of 1.0 seconds to 60 seconds, for mixing of polyethylene-containing polyolefin powder with a plasticizer to produce a mixed slurry, a step of extruding the mixed slurry and cooling it to solidification to process it into a cast sheet, and a step of biaxially stretching the cast sheet to an area increase factor of 20 to 200.
Claims11
An electricity storage device separator comprising a polyolefin microporous membrane that is used as a separator for an electricity storage device comprising an ultra-high molecular weight polyethylene (UHMWPE), wherein a degree of crystallinity (X) of all polyethylenes in the polyolefin microporous membrane is 80 to 99% as measured by X-ray diffraction (XRD), when calculated by the following formula:
- X={I(110)+I(200)}/{I(110)+I(200)+Iamr}
- wherein I(110) is the area of the (110) plane diffraction peak, I(200) is the area of the (200) plane diffraction peak and Iamr is the area of amorphous peak, and the crystallite size of all polyethylenes in the polyolefin microporous membrane is 14.2 to 40.0 nm as measured by XRD,
- wherein the cross-sectional crystal orientation of the polyolefin microporous membrane is 0.80 to 0.99,
- wherein the thickness of the polyolefin microporous membrane is 5 μm or greater and 15 μm or smaller, and
- wherein the polyolefin microporous membrane is produced by a method comprising the following steps:
- (1) a mixed slurry producing step in which a continuous mixer is used under conditions with a temperature of 20° C. to 70° C., a shear rate of 100 seconds−1 to 400,000 seconds−1 and a residence time of 1.0 seconds to 60 seconds, for mixing of a plasticizer with a polyolefin powder containing polyethylene (PE), to obtain a mixed slurry;
- (2) an extrusion step in which the mixed slurry is loaded into a twin-screw extruder and extruded to produce a resin composition;
- (3) a step of extruding the resin composition into a sheet and cooling to solidification to produce a cast sheet;
- (4) a step of biaxially stretching the cast sheet with an area increase factor of 50 to 150 to form a stretched sheet;
- (5) a step of extracting the plasticizer from the stretched sheet to form a porous body;
- and
- (6) a step of heat treating the porous body at a temperature below a melting point of the porous body, wherein the step of heat treating includes stretching the porous body.
Dependencies are inferred from the claim text.